n. — historical, Politics
an act of the British Parliament, passed in 1840 and proclaimed 10 February 1841, that united Upper and Lower Canada into the Province of Canada.
Type: 4. Culturally Significant — The term Act of Union is not unique to Canada, as other acts of union have been enacted, such as the Act of Union (May 1, 1707) unifying England and Scotland or the Acts of Union of 1800 by the British and Irish parliaments, unifying England and Ireland. See Chart 1. In the Canadian context, the term is used in reference to the 1840 treaty that united Upper Canada and Lower Canada as the Province of Canada. In 1867 the British North America Act replaced the Act of Union.
See also COD-2, s.v. "Act of Union", which is marked "Canadian History", Gage-1, s.v. "Act of Union", ITP Nelson, s.v. "Act of Union".