By winning the Revolutionary War, the United States secured recognition of its independence and gained control of land east of the Mississippi River. The Treaty of Paris doubled the area of the original 13 colonies.
"...that these United Colonies are, and of right ought to be, free and independent States." Declaration of Independence, 1776
This map shows each current state by its primary acquisition. CO, WY, and MT actually span multiple treaties. See notes.
President Thomas Jefferson purchased the vast Louisiana Territory from France, nearly doubling the country's size. Napoleon, needing funds for his European wars, sold the land for a bargain.
"The sale assures forever the power of the United States, and I have given England a rival who will sooner or later humble her pride." Napoléon Bonaparte
The Convention of 1818 fixed the U.S.–Canada boundary at the 49th parallel from the Great Lakes to the Rockies. Britain ceded the Red River Basin south of that line—present-day northern Minnesota and North Dakota.
"...the line of 49 degrees shall be the boundary." Convention of 1818
Spain ceded East and West Florida to the United States. The treaty also settled the western boundary of the Louisiana Purchase and saw Spain relinquish its claim to the Pacific Northwest.
"Spain must either control Florida or cede it to the United States." Secretary of State John Quincy Adams
The independent Republic of Texas became the 28th state. Texas had won independence from Mexico in 1836, and its annexation extended the U.S. to the Rio Grande—setting the stage for war with Mexico.
"The Republic of Texas is no more." Texas President Anson Jones, 1846
The U.S. and Great Britain peacefully divided the Oregon Country at the 49th parallel. Expansionists had cried "54°40' or Fight!"—but the compromise avoided war.
"The Country is ours. The tide of civilization must and will roll over it." Senator Thomas Hart Benton
The Mexican–American War ended with Mexico ceding California, Nevada, Utah, and parts of four other states. America now spanned the continent.
"We take nothing by conquest. Thank God." General Ulysses S. Grant (sarcastically)
A strip of land in southern Arizona and New Mexico, purchased from Mexico for a southern transcontinental railroad route. The last territorial addition to the contiguous United States.
"For the great object of a railroad to the Pacific, its value is inestimable." Senator Solomon W. Downs
Secretary of State William Seward bought Alaska from Russia. Critics mocked it as a frozen wasteland. It would later prove rich in gold, oil, and strategic value.
"...a polar bear garden." Critics of the purchase
Victory over Spain brought overseas territories: Puerto Rico, Guam, and the Philippines. Hawaii was also annexed the same year. The United States became a global colonial power.
"It has been a splendid little war." Secretary of State John Hay
American Samoa (1900), the U.S. Virgin Islands (1917), and Pacific trust territories rounded out American expansion. Alaska and Hawaii became the 49th and 50th states in 1959.
"I yield my authority… to avoid the loss of life." Queen Lili'uokalani, 1893
Contemporary rhetoric — no actual territorial changes
President Trump vowed to "take back" the Panama Canal, renewed interest in Greenland, and floated making Canada the 51st state. Denmark's Prime Minister: "Greenland is not for sale."
"We will pursue our Manifest Destiny into the stars." Donald Trump, 2025
This map assigns each modern state to its primary acquisition, which obscures cases where a state's territory came from multiple treaties:
This visualization maps territorial expansion from the perspective of the United States government. These lands were—and remain—the ancestral homelands of hundreds of Indigenous nations whose sovereignty, displacement, and treaty rights are not represented here.
Map data: US History Maps (CC BY-SA 3.0), Natural Earth
Have better map data—especially per-acquisition boundaries? Contributions and corrections are welcome on GitHub.