So, amphetamines.
OTL they were discovered in the 1880s... but then, bizarrely, they just sat around for the next 40 years, a laboratory curiosity with no known use. Their pharmacological significance wasn't appreciated until the 1920s!
Now, once this /was/ understood, America's young pharmaceutical industry promptly began marketing cheap amphetamines to the masses. Smith Kline French (ancestor of today's GlaxoSmithKline) led the way with the introduction of "Benzedrine", conveniently available as a pill or in an inhaler. Benzedrine was an over-the-counter drug that could be purchased without a prescription. For a few glorious years, it was a dime a dose in any drugstore in America. Good times, good times.
This of course led to to America's first mass outbreak of amphetamine addiction in the 1930s. By 1938, hundreds of thousands of Americans were hopelessly hooked on uppers, unable to get through the day without their Benzedrine tablets or a few snorts from the inhaler. But this first golden age of amphetamines came to a sudden end that same year, when the freedom-hating socialists in Roosevelt's Food and Drug Administration declared amphetamines a Substance of Special Interest and moved it to the prescription-only category. (Over, let it be noted, the vigorous protests of Smith Kline, who insisted that Benzedrine was not only completely harmless but a positive lifesaver to small children and the elderly.)
So, the POD: WI the pharmacological effects of amphetamines had been realized 20 years earlier?
There's really no reason this couldn't have happened. Amphetamines aren't particularly hard to synthesize, and mass production was well within the capabilities of Edwardian-era chemistry. OTL the issue seems to have been that they were originally a plant derivative (from the ephedra bush) and those were just out of style for a generation or so as the first great wave of synthetic drugs came online. But all it would really take is one researcher zigging this way instead of that. So let's say it happens [handwave]. Amphetamines are rediscovered around 1908, and Benzedrine gets marketed commercially in 1912.
Now what?
1) By the latter years of WWI, you have mass deployment of amphetamines for airmen and soldiers. Amphetamine highs and crashes make life in the trenches even more interesting than iOTL. And then after the war, the returning veterans can add withdrawal symptoms to PTSD and general alienation! Organizational meetings of the American Legion should be extra fun in this TL.
2) OTL the nosy-parker nanny-state do-gooders of the New Deal made amphetamine a controlled substance. TTL, woo, the roaring 20s! I think that the federal government of Harding, Coolidge and Hoover is going to be very slow to respond to amphetamines as a social issue -- especially since, with doughboys as the vector, it's going to be disproportionately a vice of middle class white folks. And, hey, Prohibition has left a void. So I think we could see a long decade in which alcohol is illegal but speed can be purchased like chewing gum.
3) So, the Roaring Twenties. (Maybe more like the Shrieking Twenties in this TL?) Who gets hooked?
(One likely candidate: young Ayn Rand. OTL she got hooked on prescription Benzedrine in 1942, was on and off it for over a decade, and then was just a full-blown no-holds-barred addict for the last dozen years of her life. TTL that probably gets accelerated. So, whatever else you can say about this TL, it's probably a world without _Atlas Shrugged_.)
Thoughts?
Doug M.