The Canadas were merged into a single entity in 1841, shortly after
Report on the Affairs of British North America. His report held several recommendations, most notably union of the Canadas. Acting on his recommendation, the British Parliament passed the Act of Union 1840. The Act went into effect in 1841, uniting the Canadas into the Province of Canada
.
The terms "Lower" and "Upper" refer to the colony's position relative to the headwaters of the St. Lawrence River.
The two colonies were created in 1791 with the passage of the
Loyalists from the American Revolutionary War, the Province of Quebec was divided into two new colonies, consisting of Lower and Upper Canada. The creation of Upper Canada was in response to the influx of United Empire Loyalist settlers, who desired a colonial administration modelled under British institutions and common law, especially British laws of land tenure. Conversely, Lower Canada maintained most of the French Canadian institutions guaranteed under the Quebec Act, such as the French civil law
system.
In 1838
British Parliament would eventually act on the former suggestion, with the passage of the Act of Union 1840. The Act of Union went into force in 1841, and saw the Canadas united into the Province of Canada
. However, the Act did not establish responsible government, which was not introduced until 1848.