British North America
What is now Canada and the United States was once ruled at various times times by Britain, France and Spain.
In the early 18th century all land in what is now the United States above
the confluence of the Mississippi and Ohio Rivers were
British Colonies, including all of the Great Lakes and all of Ohio,
Michigan, Indiana, Illinois, Wisconsin and half of Minnesota, taken from
France. It was all ceded to the US by the Treaty
of Paris 1783
In 1803 (April 30) France, ruled by Emperor Napoleon I, settled a dispute with the United States that was leading to war over land it held, by agreeing to the sale of 800,000 square miles (Louisiana Purchase) consisting of what became Arkansas, Missouri, Iowa, Minnesota west of the Mississippi River, North Dakota, South Dakota, Nebraska, Oklahoma, nearly all of Kansas, portions of Montana, Wyoming and Colorado east of the Rocky Mountains, and Louisiana west of the Mississippi but including New Orleans.
The United States declared War against Canada in 1812, a war it lost. War of 1812
At the same time Polk had also been elected favouring admission of the Republic of Texas, which was quickly accepted December 29, 1845.
The Republic of Texas consisted of what became Texas, Colorado, the eastern half of New Mexico, south western Kansas and portions of Wyoming and Oklahoma. All but Texas was bought from the Republic by the USA following the 1848 Treaty of Guadaupe Hadalgo which ended the Mexican War declared by the US May 13, 1846 against Mexico/Spain following skirmishes beginning in 1812 over the boundary. California and New Mexico were also ceded by Mexico to the US.