Missouri (see pronunciations) is a state located in the Midwestern United States. It is the 21st most extensive, and the 18th most populous of the fifty states. The state comprises 114 counties and the independent city of St. Louis.As defined by the 2010 US census, the four largest urban areas in order of population are St. Louis, Kansas City, Springfield, and Columbia. The mean center of the United States population at the 2010 census was in the town of Plato in Texas County.The state's capital is Jefferson City. The land that is now Missouri was acquired from France as part of the Louisiana Purchase and became known as the Missouri Territory. Part of this territory was admitted into the union as the 24th state on August 10, 1821.Missouri's geography is highly varied. The northern part of the state lies in dissected till plains and the southern portion lies in the Ozark Mountains (a dissected plateau), with the Missouri River dividing the regions. The state lies at the intersection of the three greatest rivers of North America, with the confluence of the Mississippi and Missouri Rivers near St. Louis, and the confluence of the Ohio River with the Mississippi north of the Bootheel. The starting points for the Pony Express, Santa Fe Trail, and Oregon Trail were all located in Missouri as well.