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 met…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.