Final answer:
The British North America Act came into effect in 1867, unifying several colonies into the Dominion of Canada under self-governance while remaining part of the British Empire.
Step-by-step explanation:
The British North America Act came into effect in 1867. This act was significant in the formation of Canada, as it united the colonies of Nova Scotia, New Brunswick, and the Province of Canada (which included Ontario and Quebec) into the Dominion of Canada. The Dominion was granted the right to govern itself, though it remained part of the British Empire with Queen Victoria as the monarch. This pivotal moment is remembered as a foundational event in Canadian history.