Kansas is a U.S. state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa tribe, which inhabited the area. n 1803, most of modern Kansas was secured by the United States as part of the Louisiana Purchase. Southwest Kansas, however, was still a part of Spain, Mexico, and the Republic of Texas until the conclusion of the Mexican-American War in 1848.