The 15 Territorial Expansions That Created the Modern United States
From its momentous beginning in 1776 with the Declaration of Independence, the United States has continued on a century-plus-long westward expansion by acquiring territory through wars, coercion, and some very advantageous real estate opportunities. The last of these gains was made in 1976 in the Pacific, with the formalization of Northern Mariana Islands nation as a U.S. Territory.
Westward-Ho! As vast tracts of the North American continent were added to the U.S., pioneers, settlers and prospectors made their way west, while Congress simultaneously established statehood for the new areas. Statehood recognition for all 50 states took a total of 172 years - beginning in 1787 when Delaware (1st), Pennsylvania (2nd), and New Jersey (3rd) joined, and ending with Hawaii in 1959.
MAJOR TERRITORIAL EXPANSIONS THAT SHAPED THE U.S.
DECLARATION OF INDEPENDENCE
July 4, 1776
A declaration the 13 colonies were no longer a part of Britain. The document listed grievances against King George III's government. And importantly, by declaring themselves a separate country, the colonies could enter into an important alliance with Louis XVI's French government for help in the battles to come.
TREATY OF PARIS
September 3, 1783
This treaty marks the official end of the Revolutionary War and the formal recognition of the colonies as a country. In the agreement, the new United States of America also acquires from Britain the lands west of the colonies and east of the Mississippi River. This added land instantly doubles the size of the country.
LOUISIANA PURCHASE
April 30, 1803
For $15,000,000, the United States purchased from France territory that again doubles the size of the country. France had established permanent settlements in the Mississippi Valley since 1682. The sale helped finance France's Napoleonic Wars which would go from 1803-1815.
TREATY OF 1818
October 20, 1818
Established a formal border between the United States and the British Canadian territories along what is the 49th Parallel North.
Side Note: Canada will not formally be a country until 1870. Until then it exists as a combination of indigenous tribal lands, British Crown lands, and Rupert's Land, which were territories granted by King Charles II to the Hudson Bay Company. And Mexico, known as New Spain by its 16th-century conquerors, would gain its independence through an 11-year war with Spain.
ADAMS-ONÍS TREATY
February 22, 1819
After ongoing U.S. incursions into Florida including Andrew Jackson's Seminole War of 1817, Spain decided it was not able to defend the territory of Florida and some adjacent Gulf Coast. The treaty accomplished two things: it ceded territory to the U.S., and established a formal border between the United States and New Spain (Mexico).
TEXAS ANNEXATION
December 29, 1845
Added the Republic of Texas and lands that would later make up the states of New Mexico, Colorado, and Wyoming.
OREGON TREATY
June 15, 1846
This agreement with Britain extended the 49th Parallel border westward to the Pacific Ocean, adding the territories that would become Idaho, Oregon and Washington State.
TREATY OF GUADALUPE HIDALGO
February 2, 1848
Also known as the Mexican Cession, for $15,000,000 the U.S. purchased territories from Mexico that would later form California, Nevada, Utah, and parts of Arizona and New Mexico. The exchange was part of the larger peace settlement ending hostilities of the 1846-48 Mexican-American War.
GADSDEN PURCHASE TREATY
December 30, 1853
For $10,000,000, Mexico agreed to sell these southern lands to the U.S., which helped the country establish a defined border from the Gulf of Mexico to the Pacific Ocean. This acquisition also gave railroad developers a needed flat route for a line that would run from Texas to California.
ALASKA PURCHASE TREATY
March 30, 1867
A land purchase from Russia for $7,200,000. The reasons for the sale, as with many far off territories included the economic cost of maintaining and defending the area, as well as other internal considerations such as a country's finances. In this case, the Tsar's regime was in need of cash.
TREATY OF PARIS
December 10, 1898
Part of the peace settlement ending the 1898 Spanish-American War, the treaty gave the U.S. new strategic territories in the Caribbean with Puerto Rico, and in the Pacific with Guam and the Philippines.
TREATY OF CESSION OF TUTUILA / TREATY OF BERLIN
December 2, 1899
An agreement with the chiefs of this Pacific Archipelago established the Island of Tutuila, in Samoa as a United States territory. This was part of a larger negotiation between the U.S., Britain and Germany, all of whom wanted the islands for strategic reasons. An earlier 1898 agreement, the Treaty of Berlin, failed to achieve that goal.
ANNEXATION OF THE REPUBLIC OF HAWAII
July 7, 1898
Driven by aggressive business interests, its value as a strategic naval base, various constitutional changes and a bloodless coup, the Republic of Hawaii became a part of the United States.
TREATY OF THE DANISH WEST INDIES
August 4, 1916
The Kingdom of Denmark sells what will become the U.S. Virgin Islands to America for $25,000,000. For the U.S. this represented a strategic military gain in the Caribbean. For the islands' residents, they enjoy U.S. citizenship, but cannot vote in Presidential elections.
COVENANT TO ESTABLISH A COMMONWEALTH OF THE NORTHERN MARIANA ISLANDS IN POLITICAL UNION WITH THE U.S.
March 24, 1976
Since 1947, following WWII, the U.S. was the trustee of the island nation. Towards the later part of the 20th century, the island nation wanted a closer political relationship with the U.S., spurring the development of this agreement, which allowed for self-government, while giving the U.S. sovereignty over the country.
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