Territorial changes of the United States

This is a United States territorial acquisitions and conquests list, beginning with American independence. Note that this list primarily concerns land the United States acquired from other nation-states. Territorial acquisitions derived from the displacement of Native Americans are not listed here.

The 1783 Treaty of Paris with Great Britain defined the original borders of the United States. It generally stretched from the Eastern Seaboard to the Mississippi River in the west. There were ambiguities in the treaty regarding the exact border with Canada to the north that led to disputes that were resolved by the Webster–Ashburton Treaty in 1842. Beginning in the late 18th century, the new nation organized areas west of the Original thirteen states into several United States territories, setting a template for future expansion.

The Louisiana Purchase in 1803, was negotiated with Napoleon during the presidency of Thomas Jefferson; the territory was acquired from France for $15 million (equivalent to $240 million in present-day terms). A small portion of this land was ceded to Britain in 1818 in exchange for the Red River Basin. More of this land was ceded to Spain in 1819 with the Florida Purchase, but was later reacquired through Texas annexation and Mexican Cession.

West Florida was declared to be a U.S. possession in 1810 by President James Madison after the territory had declared its independence from Spain. Madison ordered the U.S. Army to take control. Six weeks later, the army entered and occupied the capital, St. Francisville, putting an end to the republic after 74 days of independence. Spain did not relinquish its claim to sovereignty (see West Florida controversy) until ratification of the Adams-Onís Treaty. General Andrew Jackson personally accepted the delivery of West Florida from its Spanish governor on July 17, 1821.

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