Original inhabitants of the region include the Arapaho, Crow, Lakota, and Shoshone. Southwest Wyoming was claimed by the Spanish Empire and then as Mexican territory until it was ceded to the U.S. in 1848 at the end of the Mexican–American War. The region acquired the name "Wyoming" when a bill was introduced to Congress in 1865 to provide a temporary government for the territory of Wyoming. The name had been used earlier for the Wyoming Valley in Pennsylvania, and is derived from the Munsee word "", meaning "at the big river flat".