In which year did Americans attempt to invade Canada?

The year 1775 is significant in American history as it marks the first attempts made by the American revolutionary forces to invade Canada. This occurred during the early stages of the American Revolutionary War when the Continental Congress sought to take advantage of British weaknesses and extend the conflict into Canada. The thinking at the time was that the French-speaking Canadians might join the revolution against British rule.

Richard Montgomery led the invasion that attempted to capture Quebec, which was a critical stronghold. Although the campaign showed initial promise, it ultimately resulted in a retreat and was costly for the American forces due to attrition and harsh winter conditions. The efforts to invade Canada that year represent an early facet of American military strategy in the Revolutionary War.

The other years listed, 1774, 1776, and 1777, did not have significant attempts to invade Canada by Americans in the same organized military sense as 1775, making this year the correct answer to the question.