The colonies and territories of the British Empire in continental North America were referred to as British North America. An Act of the British Parliament called the British North America Act (July 1, 1867) formed the Dominion of Canada from the Province of Canada, New Brunswick, and Nova Scotia. British North America included Canada, New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland, Vancouver Island and British Columbia. The colonies were geographically, politically and economically separate from each other.
Britain was tired of maintaining its colonies and the costs defending British North America, were burdens that British politicians did not approve. British North America was also facing the outbreak of the American Civil War which was a threat to the safety of the colonies. Colonial politicians felt the best way to avoid being absorbed by the United States was to unite. After 1791, British North America took on outlines that it would carry into the Canadian federal union of 1867.
With the passing of the British North America Act in 1867, Canada became a Dominion in the British Commonwealth. It was not a fully independent country, though. It remained a colony of Britain for many years.