How the United States Expanded: Major Territorial Acquisitions of the 19th Century

The United States grew from the original thirteen colonies to a continental nation primarily during the 1800s through purchases, treaties, and war.

Key Acquisitions

• 1783 Treaty of Paris – Independence and the original territory.
• 1803 Louisiana Purchase – Doubled the nation, acquired from France.
• 1819 Florida Purchase – Acquired from Spain.
• 1845 Texas Annexation – Republic of Texas joined the Union.
• 1846 Oregon Treaty – Settled boundary with Britain at the 49th parallel.
• 1848 Mexican Cession – Southwest and California after Mexican–American War.
• 1853 Gadsden Purchase – Southern Arizona/New Mexico from Mexico.
• 1867 Alaska Purchase – Bought from Russia.
• 1898 Annexation of Hawaii – Added Pacific territory.

These steps established the current contiguous U.S. plus Alaska and Hawaii.