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.
The state takes its name from the Ohio River. The name originated from the Iroquois language word ohi-yo, meaning "great river" or "large creek". Partitioned from the Northwest Territory, the state was admitted to the Union as the 17th state (and the first under the Northwest Ordinance) on March 1, 1803. Ohio is historically known as the "Buckeye State" after its Ohio buckeye trees, and Ohioans are also known as "Buckeyes".