In pre-colonial times, the Neutral Indians used much of the land but were gradually driven out by the Five Nations (Iroquois) who were allied with the British against the Huron and their French allies. A member of the Iroquois Confederacy provided the route and name for Mohawk Road, which originally included King Street in the lower city.

In 1784, about 10,000 United Empire Loyalists settled in Upper Canada (what is now southern Ontario), chiefly in Niagara, around the Bay of Quinte, and along the St. Lawrence River between Lake Ontario and Montreal. They were soon followed by many more Americans, some of them not so much ardent loyalists but attracted nonetheless by the availability of inexpensive, arable land. At the same time, large numbers of Iroquois loyal to Britain arrived from the United States and were settled on reserves west of Lake Ontario.