Lemmon is a city in Perkins County, South Dakota, United States. The population was 1,227 at the 2010 census.
Lemmon is named after George Ed Lemmon, a cattleman, who founded the town in 1906.
Lemmon is located at 45°56′22″N 102°9′36″W (45.939375, -102.160128). According to the United States Census Bureau, the city has a total area of 1.04 square miles (2.69 km2), all land.
Lemmon's north border is the Adams County, North Dakota, boundary. To the east of Lemmon is Corson County and Standing Rock Indian Reservation.
Lemmon's history as a town started in 1902 with the U.S. government's forced leasing of about 800,000 acres of Standing Rock Indian Reservation lands to cattle rancher George Ed Lemmon.
In 1919, Lemmon became a sundown town, prohibiting African Americans from living there.
As of the census of 2010, 1,227 people, 567 households, and 319 families resided in the city. The population density was 1,179.8 inhabitants per square mile (455.5/km2). The 732 housing units averaged 703.8 per square mile (271.7/km2). The racial makeup of the city was 96.3% White, 0.1% African American, 1.9% Native American, 0.2% Asian, 0.1% from other races, and 1.5% from two or more races. Hispanics or Latinos of any race were 0.7% of the population.