Different crops and the viability of slavery

[Socrates]

I'm trying to find evidence of which crops were much more profitable with slavery, and for which crops free labour was competitive.

The map available here suggests slavery was heavily preferenced in crops along the River Missouri, and potentially would be if it had been allowed heading into Nebraska:

http://www.sonofthesouth.net/slavery/slave-maps/us-slave-map-750.jpg

Obviously cotton and sugar are the obvious ones are preferencing slavery. Tobacco seems to be a more marginal case. What about maize, wheat etc? Would there have been more slavery in the old North West had attitudes and legal restrictions been different. What about crops in Latin America, had chattel slavery occurred there?

I'm also interested in how this may have been different for non-agricultural activities. In Southern Brazil they used slaves for tending livestock, which seemed competitive with the free labour of the same economy in Uruguay. The silver mines of Bolivia obviously used slaves in a big way - could this have happened in California during the gold rush?

 

[snerfuplz]

What about crops in Latin America, had chattel slavery occurred there?

You should look at 1900 Mexico under Porfirio Diaz especially the henequen (hemp) farmers of the Yucatan. Chattel slavery was very much alive before the 1910 Revolution.

 

[Socrates]

Interesting - I had always been under the impression it was serfdom rather than slavery in Yucatan.

 

[archaeogeek]

You should look at 1900 Mexico under Porfirio Diaz especially the henequen (hemp) farmers of the Yucatan. Chattel slavery was very much alive before the 1910 Revolution.

The problem of slavery for hemp is the same as slavery for wheat, it's a staple crop that's not particularly labor intensive. Ditto for maize. You're not going to be running slavery for non cash crops except maybe rice (which was a 19th century fad in some of the southern states). Serfdom, yes, but that's not chattel slavery.

 

[Jared]

I'm trying to find evidence of which crops were much more profitable with slavery, and for which crops free labour was competitive.

The answer to that question is that it wasn't the competition between slave and free labour which mattered. For pretty much any North American crop which could be sold for a profit, slave labour was at least as productive as free hired labour. (Not always as productive as self-employed farmers, except for gang labour conditions.)

The situation in North America - and in most New World slavery - was that there was a chronic labour shortage. Land was cheap (except, eventually, on some of the smaller sugar islands), and labour was very expensive. This was what made slavery viable in the first place - labour was so expensive that finding a way to make it compulsory was useful. (Free farmers had the perpetual problem that they couldn't get reliable hired labour, since the hired labour would leave to start their own farm on cheap land, or go on strike during the harvest.)

So what you had was a large group of would be slaveowners bidding for a limited supply of slaves. This concentrated the slave labour into the crops which were the most profitable, rather than simply ones where slave labour out-competed free labour.

For New World slavery as a whole, sugar was far and away the most profitable crop. It sucked in the largest percentage of slave imports for more or less the whole slave period. Slavery could be and was used profitably on a range of other crops - coffee, cocoa, tobacco, indigo, hemp, cotton, rice, wheat. But the relative profitability of these crops varied a lot, both between crops and over time, and this affected the usage of slave labour.

For North America, during the colonial period the three biggest crops were tobacco, rice and indigo. Cotton was a minor crop since only long-staple cotton could be grown profitably until the (re)invention of the cotton gin, and long-staple cotton could only be grown in a few coastal areas. Hemp was a profitable but minor crop, and there was some slave labour employed in wheat (and other small grains).

After the American Revolution, the indigo market collapsed since it depended on British subsidies. Rice went into relative decline too, since European tastes were gradually shifting away from it. Tobacco remained profitable on the whole, although the tobacco rice rose and fell - some Virginia plantations switched back and forth between tobacco and wheat depending on relative prices. Hemp production expanded too, into Kentucky and Missouri, but it was still a relatively minor crop. Sugar production also rose a bit as the US expanded into regions where the climate permitted its growth (Florida and other parts of the Gulf Coast).

Everything, though, remained secondary to cotton after the development of the cotton gin. Cotton was the boom crop of the nineteenth century, which offered a return on investment that nothing else could match, and it sucked up most of the available slave labour. Cotton pushed slave prices high enough that it drew much of the available labour out of other crops (eg tobacco) - even though tobacco could be grown for a profit with slave labout, cotton could be grown for a bigger profit.

Obviously cotton and sugar are the obvious ones are preferencing slavery.

Cotton was king for obvious reasons. Sugar was also crazily profitable, but more restricted in where it could be grown.

Tobacco seems to be a more marginal case. What about maize, wheat etc?

Tobacco was profitable, but not in the same league as cotton. Wheat was grown as a cash crop with slaves in Virginia, and to a lesser degree Kentucky and Missouri.

Slaves actually grew a fair amount of maize - many large plantations had slaves grown their own maize during off-peak periods. It was just that this maize was mostly used to feed the slaves; it was just the cotton that was exported, since the price was higher. A few big plantations imported food, but many - the majority, if I remember correctly - produced it on-site.

Would there have been more slavery in the old North West had attitudes and legal restrictions been different.

With the supply of slaves limited and cotton offering greater profitability, it didn't really matter much what the attitudes and legal restrictions were. If cotton production were suppressed for some reason, then wheat and hemp would have been viable slave-grown crops, although the return on investment would have been lower than with cotton.

What about crops in Latin America, had chattel slavery occurred there?

Well, chattel slavery was around in most of Latin America, so yes, it could be used for crops there too. Sugar remained the biggest use overall, but coffee and cocoa (among others) were viable slave crops too. Tropical fruit could be grown on plantations, too, although slavery had mostly been abolished by the time that refrigeration allowed those fruit to be exported effectively.

Sisal (henequen) was probably the biggest other potential crop (see below).

I'm also interested in how this may have been different for non-agricultural activities. In Southern Brazil they used slaves for tending livestock, which seemed competitive with the free labour of the same economy in Uruguay. The silver mines of Bolivia obviously used slaves in a big way - could this have happened in California during the gold rush?

About 20% of Brazil's slaves worked in mining, so yes, it was possible. Slavery was tried a bit during California, but free workers opposition kept it from being used a lot. Slavery was used for gold mining in Georgia during earlier times. It was considered for New Mexico mining, too, but cotton kept slave prices high enough that it wasn't really competitive to do so.

Slaves were used for livestock in some North American plantations too, although not on a large scale. (Cattle in northern Virginia, for instance.)

Slaves were also used in various industrial and proto-industrial pursuits in the USA during the nineteenth century, too. Lumber, construction, shipbuilding, turpentine extraction and distillation, and so on. But the bulk of the slave labour force remained in cotton, because of its profitability.

You should look at 1900 Mexico under Porfirio Diaz especially the henequen (hemp) farmers of the Yucatan. Chattel slavery was very much alive before the 1910 Revolution.

Sadly, yes. What was done to the Yaqui was abominable.

Interesting - I had always been under the impression it was serfdom rather than slavery in Yucatan.

Much of what happened in the Yucatan was de facto serfdom (for the native Maya). But after the Yaqui in Sonora tried to revolt during the 1880s, many of them were forcibly deported to Yucatan, where a lot of them were sold as slaves.

The problem of slavery for hemp is the same as slavery for wheat, it's a staple crop that's not particularly labor intensive.

Henequen, which snerfuplz is referring to here, is not the same thing as the hemp grown in North America. It's a different plant (Agave fourcroydes and Agave sisalana) grown in the Yacatan and elsewhere, and which yielded a very high quality fibre which could be sold profitably. It was well-suited for gang labour, and at least for the Yaqui, was grown in slave conditions.

Of course, normal hemp and wheat could also be grown profitably with slavery (see above).

Ditto for maize. You're not going to be running slavery for non cash crops except maybe rice (which was a 19th century fad in some of the southern states). Serfdom, yes, but that's not chattel slavery.

Rice was a cash crop from the seventeenth century onward, and one of the three biggest plantation crops in colonial North America. It was such a high-status crop that it could be grown profitably in South Carolina (and later Georgia) and exported to Europe.

 

[Socrates]

Jared - This is absolutely fantastic information! I have a few more questions, if you don't mind.

What were the limits to where cotton, sugar, tobacco and rice could be grown in the Americas? Cotton needed tropical temperatures, but it didn't seem to be grown all that much outside the US. Was henequen a better crop to grow in Mexico, or were they just being inefficient? If you'd have had ruthlessly efficient plantocrats outside the US south, do you think the crop distribution across the Americas would have changed much? Sugar was the main slave crop in Brazil - how come it didn't soak up all the slaves there?

If I understand it right, tobacco and rice both needed wetlands, so could only be grown around marshy coastal areas. The map I linked showed a concentration of slaves around the feed-in rivers to the Mississippi - what crop was this? How far north could it potentially spread?

I'm also interested in how things could change if the price of slaves dropped. After the transatlantic route was banned, was there ever an push to import Native Americans from New Spain or New Grenada? Would it have been viable to have a reverse Atlantic route - taking Native Americans to work on slave plantations in Africa where they can't disappear into the bush?

 

[MNP]

If you take Native Americans to Africa they die real fast. Even after lots of generations of disease immunity they're still going to drop fast. Ability to survive in Africa goes north to south, the farther away you are the more deadly the interior is to you. That's one reason the Europeans didn't push deep into the interior until certain technology advances were made. Before that it was more trouble than it was worth.

 

[mrmandias]

Wheat in particular yielded to early mechanization and therefore could be very profitable in a free labor/expensive labor environment.

Flip side of the argument that cotton was the *most* profitable use of slave labor is looking at what the most profitable crops were in an environment of cheap land and expensive free labor.

 

[Socrates]

Does anyone know why inland Africa is so much more deadly than the inland areas of central and south America?

 

[Jared]

Jared - This is absolutely fantastic information! I have a few more questions, if you don't mind.

What were the limits to where cotton, sugar, tobacco and rice could be grown in the Americas?

I don't have detailed information about all of those. Most of what I know about slavery and plantation agriculture has come from how and where it was used and crops were planted. That is, there may well have been other areas where the crops could be grown, but weren't cultivated in OTL for one reason or another.

Cotton needed tropical temperatures, but it didn't seem to be grown all that much outside the US.

If you're growing cotton as an annual plant, what it actually needs is a minimum number of frost-free days to grow in. That works perfectly well in most subtropical areas, including the US South. You also don't want the soil getting too wet, which could sometimes be a problem in more tropical areas.

That said, cotton could be and was grown in other areas. Mexico, for instance, aparts of the Caribbean, and if memory serves, even a bit in Brazil.

The biggest advantage which the South had for cotton growth was lots of slave labour - gang labour in cotton enhanced productivity - and an excellent natural transportation network (waterways) which meant that it was cheaper to ship cotton from there. The development of railroads in the nineteenth century only added to those benefits.

Was henequen a better crop to grow in Mexico, or were they just being inefficient?

Henequen/sisal was the best crop in a couple of areas of Mexico - the Yucatan, principally. It was also immensely profitable in the last couple of decades in the nineteenth century, thanks to a couple of factors which didn't apply at the height of the cotton boom. This was because sisal was of most use as a fibre for rope and twine, and there was a booming market in twine thanks to things like the mechanization of wheat farming (binder twine from reapers etc).

Cotton wasn't impossible to grow in Mexico - some parts of Mexico offer about the best damn cotton land on the globe. But those parts weren't always the best connected to natural transportation nets (ie the rivers weren't as good, and railways weren't really built much). Plus, of course, there weren't slaves to use in gang labour.

If you'd have had ruthlessly efficient plantocrats outside the US south, do you think the crop distribution across the Americas would have changed much?

Hard to say. Some places like the highlands of Nicaragua and Colombia would have done very well for plantations of a variety of crops if transportation networks could be set up. In Nicaragua that would mean some improvements to the San Juan River. In Colombia, it may require railways - I'm not sure.

There's too many other variables to give a definitive answer, though.

Sugar was the main slave crop in Brazil - how come it didn't soak up all the slaves there?

Not everyone who owned slaves wanted to use them for those sort of pursuits. House slaves, domestics, artisans, etc - there were all sorts of uses. Even in the British West Indies, only something like two-thirds of the slave labour force worked in sugar-related areas.

There's also the point that sugar slaves tended to die within a handful of years, and so while sugar planters bought the majority of newly-imported slaves, those few who were bought by other planters tended to live longer, and thus formed a greater proportion of the workforce.

If I understand it right, tobacco and rice both needed wetlands, so could only be grown around marshy coastal areas.

Rice works best in very wet, low-lying areas, until someone works out how to do proper irrigation. (Irrigated rice is grown in Australia today, for instance, in what are otherwise distinctly dry areas).

Tobacco is not really dependent on wetlands. If memory serves, its requirements for rainfall are actually lower than for something like cotton, and much less than rice.

The map I linked showed a concentration of slaves around the feed-in rivers to the Mississippi - what crop was this? How far north could it potentially spread?

Not sure which feed-in rivers you mean - the Mississippi has rather a lot of tributaries. In general, though, cotton was the big crop in all but the Upper South and the border states. I don't have a source handy for the state-by-state breakdown of what else was grown in the upper south, but hemp was big in Kentucky, of lesser importance in Missouri, and wheat was also grown in both states. Tennessee and Arkansas were mostly cotton.

I'm also interested in how things could change if the price of slaves dropped.

The question would be why they drop, since that determines what the response will be. If falling cotton prices are the answer, then slave labour moves to whatever the next most profitable use(s) are.

Going by the trends which were around in the late antebellum South, that would probably be an expansion of tobacco production (especially once someone invents the cigarette rolling machine), some growth of sugar production in otherwise marginal cotton lands, maybe mining in New Mexico, and a lot of expansion into industrial and proto-industrial pursuits (urban factories and artisans, construction, turpentine, lumber etc).

After the transatlantic route was banned, was there ever an push to import Native Americans from New Spain or New Grenada? Would it have been viable to have a reverse Atlantic route - taking Native Americans to work on slave plantations in Africa where they can't disappear into the bush?

No and no, respectively. As MNP pointed out, they'd die in droves. Just too susceptible to Old World diseases. That would be bad enough in North America, and sheer absolute bloody murder in tropical Africa.

Even Europeans died in massive percentages in tropical Africa. The sailor's chant went something like this:

"The bight of Benin, the bight of Benin
Three came out, where a hundred went in."

Edit:

Does anyone know why inland Africa is so much more deadly than the inland areas of central and south America?

Because that's where primates evolved, and all of the lovely parasites, viruses, moulds and everything else has had millions of years to become very good at infecting people.

Malaria, yellow fever and sleeping sickness were probably the three biggest killers overall, and two of them made it to the Americas. But there's an endless host of other parasites, bacteria, viruses and what have you in Africa which never made it any further elsewhere. Worse than that, many of these pathogens are also specific to particular small areas, and people have developed only local resistance to them. Even a native African in, say, southern Nigeria who moved to somewhere in Cameroon would lack resistance to the local nasties there.

I also suspect (although I don't have a definite source) that the mosquitos etc in Africa are better at biting people than the ones in the Americas. That would make sense, since the mosquitos in Africa have been there longer. I do know that one reason malaria never became as big a plague in Australia is because while the local mosquitos can carry the parasite, they're not as good as transmitting it as African or SE Asian mosquitos are.

 

[Thande]

Jared, as you know everything about this, I thought I might pick your brains a little...in my own timeline, I have the invention of the cotton gin delayed until the 1830s (there is a good reason for this: someone tried to patent one earlier but was suppressed by Virginian tobacco interests). I'm wondering how the South might have looked in the 1830s without the cotton gin. I have the Carolinas still growing a lot of rice (Europe in the 1820s is mad for Chinese stuff as China has been opened to trade, so it fits) and Virginia's main export crop being tobacco, but I was wondering about the other ones you mention. America, though independent, is still tied to Britain in my TL so indigo might still be sustainable (although Britain is in no position to give subsidies anymore, it would have been until the 1810s). Also, Europe is industrialising and hungry for cotton to feed its textiles industry, so if a cotton-gin-less South is unable to keep up with demand, what other areas might step up production? Brazil, India?

I also have tropical fruit and peanuts being introduced to the OTL Georgia/Florida area rather earlier than OTL due to different trade ties to a different government in OTL Mexico/Central America. Would slavery be applicable to these crops?

 

[Nugax]

I also suspect (although I don't have a definite source) that the mosquitos etc in Africa are better at biting people than the ones in the Americas. That would make sense, since the mosquitos in Africa have been there longer. I do know that one reason malaria never became as big a plague in Australia is because while the local mosquitos can carry the parasite, they're not as good as transmitting it as African or SE Asian mosquitos are.

They're just as good at the biting, the Parasite is less optimised for their salivary glands, and the mix of Plasmodium species is different (rather than having all four like in africa, places outside will only have a subset, reducing malarial prevalence).

 

[Jared]

Jared, as you know everything about this, I thought I might pick your brains a little...in my own timeline, I have the invention of the cotton gin delayed until the 1830s (there is a good reason for this: someone tried to patent one earlier but was suppressed by Virginian tobacco interests).

In passing, while it's not impossible to delay the invention of the cotton gin by ~40 years, this is a huge change. The ramifications would be global.

Cotton textiles and mills drove a huge chunk of the industrial revolution, creating booming factories and cities in Britain and New England. Cotton textiles were also a major part of the expansion of the British Empire, allowing them a trade wedge in India and various parts of Africa, and ultimately tying the Empire closer together through economic integration. The textile industry also encouraged further innovation and technological development, too.

The social changes would be noticeable, too. Cotton emerged as the fabric of choice for the middle class, due to its feel and ease of washing (both for clothes and sheets). Cleanliness became a social issue, and perhaps (opinion is divided) a public health issue too.

I'd also be unsure whether the reason you've suggested would delay the cotton gin for so long. There were a whole slew of inventors who were working on equivalents of the cotton gin, due to the huge and obvious benefits of it. British industry was screaming out for more cotton, there was lots of empty land where short-staple cotton could be grown easily. Both wealthy individuals and governments were keen on anything which would allow cotton expansion.

If all else fails, governments ITTL might end up doing before the invention of the cotton gin something which they did after its invention in OTL: offer a substantial prize for a successful invention. Eli Whitney never did make that much money off his cotton gin invention anyway, due to the non-enforceability of the patent, but the Georgian government voted him a very large sum of money as a prize eventually. ITTL, there may well be incentives for state governments to offer prizes instead - cash in the hand is worth more than a non-enforceable patent in the bush.

But anyway, putting aside that rather long-winded tangent, on to the question.

I'm wondering how the South might have looked in the 1830s without the cotton gin.

First and biggest question is how long the international slave trade lasted. In OTL, Britain didn't abolish it until around the same time as the US did (1808), since there was no point doing it earlier. ITTL... well, remember that in OTL about half of all US slaves were brought into the country between the end of the ARW and the abolition of the slave trade in 1808. An earlier or later end to the international slave trade will have massive flow-on implications for the slave population of *North America.

I have the Carolinas still growing a lot of rice (Europe in the 1820s is mad for Chinese stuff as China has been opened to trade, so it fits) and Virginia's main export crop being tobacco, but I was wondering about the other ones you mention.

A second rice boom is possible, although rather geographically constrained in the regions it can be grown. I don't know whether rice could be grown along the southern edges of the Gulf Coast. Maybe. There wasn't much incentive in OTL since sugar and cotton were more profitable, but maybe ITTL it might happen.

Tobacco is still viable, although prices weren't consistent. You may well find that Virginian farmers were still growing wheat (and livestock, too) a bit.

Further west, hemp is still going to be a mainstay in Kentucky. That and wheat are perfectly possible to grow in Missouri, south-eastern Kansas, and for that matter southern Illinois and Indiana. (Whether they will be grown there is a political question, more than an economic one.)

Sugar can only be grown in very limited areas - principally OTL Florida and Louisiana. It would be viable there provided that cheap sugar wasn't permitted to be imported. (Cheap sugar from the British Caribbean, or Cuba, would weaken the viability of continental NA plantations.)

America, though independent, is still tied to Britain in my TL so indigo might still be sustainable (although Britain is in no position to give subsidies anymore, it would have been until the 1810s).

As soon as the subsidies stop, indigo is probably gone in less than a decade. In OTL, commercial indigo production ceased within about 8 years (from 1792 to 1800, according to Fogel). That was mostly due to the subsidies, although also because Britain turned to Indian indigo. It was also the case that indigo producers elsewhere (French and Guatemalan) could produce more harvests per year, which would further weaken the market.

Interestingly, though, with Britain and America still tied together, there's at least one other industry which may boom: turpentine.

Turpentine, pitch, tar and related products were a major industry in North Carolina during colonial days. Turpentine was almost the petroleum of its day: used in many kinds of manufacturing, as a solvent, an illuminant, and more. Most notably, resin, turpentine etc were a major source of naval stores.

In OTL, Britain drew a lot of its naval stores from colonial North Carolina and related areas. After the ARW, Britain decided (quite sensibly) that it didn't want its naval strength to be dependent on a hostile power, and looked elsewhere. It eventually lifted duties on importation of naval stores from the USA in 1840, and the turpentine industry boomed.

By 1850 in OTL North Carolina alone produced 88% of the USA's naval stores, with South Carolina and Georgia supplying most of the rest, and with major exports to Britain. The turpentine extraction and distillation was conducted almost entirely by slaves.

ITTL, with Britain and America friendly, the naval stores industry is likely to boom sooner.

Also, Europe is industrialising and hungry for cotton to feed its textiles industry, so if a cotton-gin-less South is unable to keep up with demand, what other areas might step up production? Brazil, India?

Nowhere, really, in terms of having the capacity and the cost-effectiveness to do so. Gang labour, the favourable climate and soils of the South, cheap water transport and relative proximity to Europe all gave the South an advantage that nowhere else could really match on that scale. Indian cotton was of inferior quality and too far away, and Brazil didn't have the capacity to expand that quickly. (Or the transport infrastructure, in most regions.)

As per above, you've just knocked a huge chunk out of the Industrial Revolution. There might be a bit more growth of wool and linen textiles, but nothing to match the massive industrialisation which took place with cotton growth.

Another related, slightly paradoxical point is that while you've just hurt global industrialisation, you've probably boosted Southern industrialisation. In OTL, from about the 1780s to 1815, Southern planters were investing enough of their profits in industrial and transportation projects that the South was roughly keeping pace with the North in industrialisation, on a per capita basis.

After 1815 in OTL, Southern industrialisation fell behind as more capital was invested in primary cotton production (land, slaves, and ancillary industries). ITTL, with no cotton boom, Southern investment is going to continue in industrial and transportation areas. Northern textile mills aren't going to be around as much, either. While the South lacks some of the natural resources which made the North an industrial superpower, the industrial gap between North and South is going to be a lot smaller.

I also have tropical fruit and peanuts being introduced to the OTL Georgia/Florida area rather earlier than OTL due to different trade ties to a different government in OTL Mexico/Central America. Would slavery be applicable to these crops?

Slavery is perfectly compatible with tropical fruit; it was done a bit in OTL, and could be done more. Without refrigeration, though, I'm not sure how well the fruit could be exported to the key markets - depends on the fruit and the destination.

Peanuts could be grown by slaves, of course - practically any crop could - but I don't know how useful they'd be as a cash crop, or whether slavery would offer any particular advantages.

It'd be worth checking whether peanuts were best harvested by the gang system or the task system (ie workers harvesting as a work gang, or as individuals allocated their own area). If peanuts are best harvested by gang labour, then slavery would be an advantage, as it was with cotton and wheat.

They're just as good at the biting, the Parasite is less optimised for their salivary glands, and the mix of Plasmodium species is different (rather than having all four like in africa, places outside will only have a subset, reducing malarial prevalence).

Interesting. If memory serves, there were also differences between malaria strains even within the Old World. European strains of malaria weren't as readily transmitted by African mosquitoes, and vice versa.

 

[tallwingedgoat]

Another way of suppressing the cotton industry is an earlier boll weevil infestation.

While not a crop, one potential slave industry could develope around bituminous coal in the Apalachians. This could be turned into kerosene which was a high demand lamp oil that replaced whale oil post-slavery. Of course this would require some minor advances in chemistry and lamp technology.

 

[MNP]

Another way of suppressing the cotton industry is an earlier boll weevil infestation.

Now that would be a fascinating timeline. Boll wevil arrives in Alabama in 1815 instead of 1915.

 

[Socrates]

You say that slavery was an advantage in wheat production. If you have a situation where many more slaves were imported due to a later abolition of slavery, that would mean wheat would pick up a lot of them. It seems like that would mean slavery could spread very far north... with big political consequences.

Is there any slavery could become big in Appalachia if the price fell enough? Cohee culture seemed big against it in our timeline.

As a final point, I've also heard that the price of slaves was starting to go up anyway before the slave trade was banned, due to the supply of them drying up in Africa. Is there any truth in this? Could another source be found? I'm thinking the indigenous peoples of Mexico and/or Gran Colombia.

 

[King Gorilla]

You say that slavery was an advantage in wheat production. If you have a situation where many more slaves were imported due to a later abolition of slavery, that would mean wheat would pick up a lot of them. It seems like that would mean slavery could spread very far north... with big political consequences.

Is there any slavery could become big in Appalachia if the price fell enough? Cohee culture seemed big against it in our timeline.

As a final point, I've also heard that the price of slaves was starting to go up anyway before the slave trade was banned, due to the supply of them drying up in Africa. Is there any truth in this? Could another source be found? I'm thinking the indigenous peoples of Mexico and/or Gran Colombia.

The problem is with economic viability. Slaves could be used for wheat production, but wheat isn't nearly as labor intensive, nor as profitable per unit as sugar, cotton, or tobacco especially in a labor poor environment such as North America. It would be much more profitable to use the money needed to buy a slave(s) and invest it in more land, than to use chattel labor for the planting and harvest, and have to support said slave(s) during the long winters.

 

[Socrates]

The problem is with economic viability. Slaves could be used for wheat production, but wheat isn't nearly as labor intensive, nor as profitable per unit as sugar, cotton, or tobacco especially in a labor poor environment such as North America. It would be much more profitable to use the money needed to buy a slave(s) and invest it in more land, than to use chattel labor for the planting and harvest, and have to support said slave(s) during the long winters.

There must come a point though where all the good sugar and cotton growing land was used up. At that point there would be a significant price differential between northern land and southern land, making the investment in slaves (providing they were cheap enough) and wheat slavery worthwhile?

 

[The Sandman]

The social effects of no cotton would be interesting. From what I recall from my last visit to Colonial Williamsburg, one of the things about tobacco is that you can grow it in relatively small quantities and still turn a decent profit off of it; most small farmers in colonial Virginia would have at least some land in tobacco.

A side effect of this was that the price of slaves was considerably lower than it would become after the cotton boom got into full swing, and therefore that far more people owned (and therefore regularly associated with) slaves. There also was more land available for small farmers, since the massive cotton plantations hadn't formed yet. These produced a population that had far more everyday interaction between whites and blacks, and with much less of an economic gap between any given level of the social strata.

 

[Maniakes]

The major reason that slaver labor was concentrated in cotton production in the deep South (and secondarily in tobacco, rice, and indigo) is not that other crops were inherently unprofitable with slave labor, but rather because cotton was so profitable that cotton planters bid up the price of slaves to levels that made other crops unprofitable. From ~1800 to the Civil War, there was a steady process of the slave population being moved southwards ("sold down the river") as cotton planters expanded and growers of other crops in the border south sold their slaves and switched to free labor. Since the Atlantic slave trade was banned in 1808, the supply of slaves was relatively fixed and increased demand meant higher prices.

If you want to spread slavery over a wider area and working more crops, you could either delay the ban on the Atlantic slave trade to increase the supply of slaves, or accelerate the invention of the cotton gin in order to drive more importation of slaves before the ban.

If you instead reduce the profitability of cotton (by delaying the cotton gin or introducing an environmental obstacle like an early boll weevil outbreak, as suggested upthread), you'll also get a more spread out slave population, but with very different impact on the rest of society. You'd likely see weaker political support for slavery, since slaveowners would have more of their wealth in land and less in slaves. You'd also have a somewhat smaller slave population (as cheaper slaves are more likely to be manumitted) spread over a larger area, leading to a political structure around slavery more like OTL border states than the deep South.