alternatehistory.com

It's been said that the American victory in the Revolutionary War created three nations. Of course the Americans achieved independence and began their own course of history; Britain sought out new penal colonies, laying the foundations for the Oceania states that exist today. And of course Canada was transformed by the influx of settlers, refugees really, called United Empire Loyalists. Other events during the war would have a significant impact as well.

In a convoluted way, the lack of chattel slavery on the land of England itself, combined with the tensions of the time, led to the circulation of a rumour that King George III planned to free the slaves. Of course this wasnt true; but it was a useful lie for Patriots trying to get other slaveholders on their side.
Colonial Governor Lord Dunsmore had heard the rumour, and saw how it might be used to the advantage of the colonial authorities; his Proclamation of 1775 officially made an offer of manumission for any slave who joined the British. This led to the creation of the ill-fated Ethiopian Regiment, which likely did not have enough time to train properly before being sent into battle.
However, after its destruction, Dunsmore ordered for the raising of two units of trackers and scouts from the escape slaves arriving over the lines; these companies were called the Black Company of Pioneers; and one Lt Col John Graves Simcoe eagerly sought the commission of one.
This unit never saw combat action, but as a result suffered no casualties throughout the duration of the war. They were primarily scouts, scavengers, and humanitarians, whose efforts were concentrated in upstate New York.
As the war was winding down, he encouraged many of the Black Pioneers to make use of an overland route across the Niagara river, to ensure the crown met its obligation to his valiant troops. Meanwhile, after a riding injury, Simcoe was invalided back to Britain in 1782.

The final days of the war saw a panicked scene as increasing numbers of Loyalists descended on New York. It is estimated that over 100,000 fled in the wake of the revolution; roughly half went north to Canada.
It's hard to get precise pictures but the most accurate assessments suggest that roughly 30,000 or so made their homes in the Maritime provinces; the remainder, including some three thousand Black Loyalists and 2,000 slaves, headed for Quebec.
On Nova Scotia's South Shore, in Halifax, the Saint John Valley, the borderlands between modern Quebec and New York state (the "Eastern Townships") and the area south and west around lake Ontario (the "Western Townships"), they arrived in enough numbers to transform the local character.
Before their arrival, the population of the New France territories was probably around 130,000 Europeans, maybe 5,000 of whom were British or continental Protestant in origin.

The Loyalists made up a broad cross-section of the population; although the ones who arrived in Canada tended to be from Virginia or further north; were more likely than the American population at large to be first or second generation, and more likely to be either Anglican or a member of a religious minority.
Many of those who stayed were in fact soldiers who were being offered land after their service. Most were Scottish; but many had been in Hessian and Russian brigades, and included a number of Poles, Prussians, and Russians.
They also included the Black Loyalists, some of whom used the overland route and some of whom received official evacuation.

After the Seven Years' War, "French Acadia" had been transformed, politically, into "British Nova Scotia", but to ensure stability, British colonial authorities had extended the rights to civil law, the French language in courts, government and education, and the Catholic religion in the province of Québec. The new influx of Loyalists were used to governing themselves according to British institutions, and began demanding the right to do so in their new situation. The existing colonists already had contracts, bills of exchange and other documents which would be too numerous to disentangle; in the end a compromise was proposed which would split Quebec into two colonies, Upper Canada and Lower Canada, with Upper Canada receiving all land west of the furthest west seigneurie and south of the Nipissing river.
This occurred in 1791, and a new MP from Cornwall, first elected in 1790, was appointed to be Upper Canada's first Lieutenant Governor. Resign his place in parliament, Lt Col John Graves Simcoe arrived in Kingston in the summer of 1792.

-Gzowski, Our Cultural Mosaic