Plankinton is a city in Aurora County, South Dakota, United States. The population was 707 at the 2010 census. It is the county seat of Aurora County. Plankinton was named for Milwaukee meatpacker and hotel owner John Plankinton, a friend of Alexander Mitchell, the President of the Milwaukee Road railroad. Plankinton was home to an annual wheat palace, which became a successful regional attraction and inspired the Corn Palace in nearby Mitchell, South Dakota.