Knoxville is a city in and the county seat of Marion County, Iowa, United States. The population was 7,595 at the time of the 2020 census, an increase from 7,313 in the 2010 census. Knoxville is home of the National Sprint Car Hall of Fame & Museum, located next to the Knoxville Raceway dirt track. Knoxville is located 4 miles south of Lake Red Rock and Elk Rock State Park.