Act of Union (1840)

The Act of Union in 1840 abolished the legislatures of Lower Canada and Upper Canada and established a new Legislature of Canada to replace them. The new merged colony was named the Province of Canada, with Upper Canada renamed as Canada West and Lower Canada as Canada East. Canada West, with its 400 000 inhabitants, was represented by 42 seats in the Legislature's legislative assembly, the same number as the more-populated Canada East, with 600 000 inhabitants. By the late 1850s the faster growth of the population of Canada West had reversed the situation, and many in Canada West desired representation by population instead of the equal representation mandated by the act.

Dissatisfaction with the Act of Union in both Canadas was one of the factors that led to Canadian Confederation in the 1860s.

This political union was similar in nature and in goals to the other Acts of Union enacted by the British Parliament.