Map of United States Expansion from the United States government
(click map for larger view)
American Revolution
The United States was formed as a result of the American Revolution when the thirteen American colonies revolted against the rule of Great Britain. After the war ended, the U.S. Constitution formed a new government. These thirteen colonies became the first 13 states as each ratified the Constitution. The first state to ratify the Constitution was Delaware on December 7, 1787.
Northwest Territory
After the Revolutionary War, the United States gained control of large sections of frontier land to the west of the 13 colonies. At first this frontier land was organized into large territories such as the Northwest Territory. Over time, many of these territories became states such as Kentucky, Tennessee, and Ohio.
Louisiana Purchase
In 1803, President Thomas Jefferson bought a large area of land from France called the Louisiana Purchase. It nearly doubled the size of the country. This land eventually became all or part of 14 different states.
Mexican-American War
The large land of Texas became part of the United States after declaring its independence from Mexico. However, soon the United States and Mexico were fighting in the Mexican-American War. After the war, the United States gained more territory from Mexico through the Treaty of Guadeloupe Hidalgo. Land from all or part of 10 states became part of the United States as a result of the war including California, Colorado, and New Mexico.
Oregon Territory
Up until the 1840s, much of the northwest was claimed by both Britain and the United States. The two countries came to an agreement in 1846 called the Oregon Treaty. This treaty gave the United States land that would later become the states of Oregon, Washington, and Idaho as well as parts of Montana and Wyoming.
Gadsden Purchase
The southern portions of Arizona and New Mexico were gained from the Gadsden Purchase in 1853.
Alaska and Hawaii
The last two states to join the Union were Alaska and Hawaii. Alaska was purchased from Russia for $7.2 million and Hawaii agreed to join the United States as the 50th state in 1959.
