Arizona states of Sonora and Baja California. Arizona is the 48th state and last of the contiguous states to be admitted to the Union, achieving statehood on February 14, 1912, coinciding with Valentine's Day. 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. Southern Arizona is known for its desert climate, with very hot summers and mild winters.
Admission to the Union an equal footing with those already in existence. Of the 37 states admitted to the Union by Congress, all but six have been established within an existing U.S. organized incorporated territory. A state so created might encompass all or a portion of a territory. When the people of a territory or a region thereof would make their desire for statehood known to the federal government, in most cases Congress passed an enabling act authorizing the people of that territory or region to frame a proposed state constitution as a step toward admission to the Union. Although the use of an