Fort Smith is the second-largest city in the U.S. state of Arkansas and one of the two county seats of Sebastian County. With a population of 80,268 at the 2000 census, it is the principal city of the Fort Smith, Arkansas-Oklahoma Metropolitan Statistical Area, a region of 288,818 residents which encompasses the Arkansas counties of Crawford, Franklin, and Sebastian, and the Oklahoma counties Le Flore and Sequoyah. Fort Smith has a sister city relationship with Cisterna, Italy, site of the World War II Battle of Cisterna fought by the United States Army Rangers commanded by Fort Smith native William O. Darby. Fort Smith lies on the Arkansas-Oklahoma state border, situated at the junction of the Arkansas and Poteau Rivers, also known as Belle Point. The city began as a western frontier military post in 1817 and would later become well-known for its role in the settling of the "Wild West" and its law enforcement heritage. In 2007, Fort Smith was selected by the US Department of the Interior to be the location of the new US Marshal Service National Museum.