Watertown is a city in and the county seat of Codington County, South Dakota, United States. Watertown is home to the Redlin Art Center, which houses many of the works of Terry Redlin, one of the nation's most popular wildlife artists. Watertown is between Pelican Lake and Lake Kampeska, from which Redlin derived inspiration for his artwork. The population was 22,655 at the 2020 census, making Watertown South Dakota's 5th-most populous city.