Between the Treaty of Paris (1783) and the Civil War, America massively extended its territory by a mix of treaty, commercial transaction and war. Successive treaties with Britain in 1818 and 1846 secured a northern border along the 49th Parallel, acquiring the Oregon Territory and large tracts of land to the west of the Great Lakes. After the Louisiana Purchase (1803) from France, Florida was acquired by the Adams–Adonis Treaty (1819). In that treaty, some territory in eastern Texas was ceded to Spain, but this minor cession was overridden when the USA proceeded to annex the whole of Texas in 1845 from Mexico. After the Mexican-American War, the Treaty of Guadalupe Hidalgo ceded, the entire southwestern corner of North America to the USA. This acquisition was rounded off to the USA’s present day borders by the Gadsden purchase of 1853.
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