Arizona is the 48th state and last of the contiguous states to be admitted to the Union, achieving statehood on February 14, 1912. Historically part of the territory of Alta California in New Spain, it became part of independent Mexico in 1821. After being defeated in the Mexican–American War, Mexico ceded much of this territory to the United States in 1848. The southernmost portion of the state was acquired in 1853 through the Gadsden Purchase.
In January 1776, it became the first of the British North American colonies to establish a government independent of the Kingdom of Great Britain's authority, and it was the first to establish its own state constitution. Six months later, it became one of the original 13 states that founded the United States of America, and in June 1788 it was the ninth state to ratify the Constitution, bringing that document into effect.