Milbank is a city in Grant County, South Dakota, United States, located along the South Fork of the Whetstone River. The population was 3,544 at the 2020 census. It is the county seat of Grant County. Milbank is the birthplace of American Legion Baseball. The program was created in Milbank in 1925 and is now enjoyed by high school aged youth on more than five thousand teams in all fifty states.