St. Peter is a city and the county seat of Nicollet County, Minnesota United States. It is 10 miles north of the Mankato – North Mankato metropolitan area. The population was 12,066 at the 2020 census. It is home to Gustavus Adolphus College. U.S. Highway 169 and Minnesota State Highways 22 and 99 are three of the city's main routes. St. Peter's sister city is Petatlán, Guerrero, Mexico.