Rapid City is the second most populous city in South Dakota after Sioux Falls and the county seat of Pennington County. Named after Rapid Creek, where the settlement developed, it is in western South Dakota, on the Black Hills' eastern slope. The population was 74,703 as of the 2020 census. Known as the "Gateway to the Black Hills" and the "City of Presidents" because of the life-size bronze president statues downtown, Rapid City is split by a low mountain ridge that divides the city's western and eastern parts, called ‘The Gap.’ Ellsworth Air Force Base is on the city's outskirts. Camp Rapid, part of the South Dakota Army National Guard, is in the city's western part. Rapid City is home to such attractions as Art Alley, Dinosaur Park, the City of Presidents walking tour, Chapel in the Hills, Storybook Island, and Main Street Square. The historic "Old West" town of Deadwood is nearby. In the neighboring Black Hills are the tourist attractions of Mount Rushmore, the Crazy Horse Memorial, Custer State Park, Wind Cave National Park, Jewel Cave National Monument, and the museum at the Black Hills Institute of Geological Research. To the city's east is Badlands National Park.