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.
South Dakota is bordered by the states of North Dakota (on the north), Minnesota (to the east), Iowa (to the southeast), Nebraska (on the south), Wyoming (on the west), and Montana (to the northwest). The state is bisected by the Missouri River, dividing South Dakota into two geographically and socially distinct halves, known to residents as "East River" and "West River".