Rapid City is the second-largest city in the U.S. state of South Dakota, and the county seat of Pennington County. Named after the Rapid Creek on which the city is established, it is set against the eastern slope of the Black Hills mountain range. Rapid City had a population of 59,607 at the 2000 census. Rapid City is known as the "Gateway to the Black Hills" and the "Star of the West". The city is divided by a mountain range that splits the western and eastern parts of the city into two.