Arkansas (pronounce [ˈɑɹkn̩ˌsɑː]) is a state located in the southern region of the United States. Arkansas shares a border with six states, with its eastern border largely defined by the Mississippi River. Its diverse geography ranges from the mountainous regions of the Ozarks and the Ouachita Mountains, which make up the U.S. Interior Highlands, to the eastern lowlands along the Mississippi River. The capital and most populous city is Little Rock, located in the central portion of the state.