St. Peter is a suburb of Mankato, Minnesota in Nicollet County, Minnesota, United States. The population was 11,196 at the 2010 census. It is the county seat of Nicollet County. U.S. Highway 169 and Minnesota State Highways 22 and 99 are three of the main routes in the city.St. Peter is part of the Mankato–North Mankato Metropolitan Statistical Area.GeographyAccording to the United States Census Bureau, the city has a total area of 5.77sqmi, of which 5.59sqmi is land and 0.18sqmi is water.Demographics2010 censusAs of the census of 2010, there were 11,196 people, 3,491 households, and 2,150 families residing in the city. The population density was 2002.9PD/sqmi. There were 3,697 housing units at an average density of 661.4/sqmi. The racial makeup of the city was 90.1% White, 3.3% African American, 0.6% Native American, 1.6% Asian, 2.3% from other races, and 2.0% from two or more races. Hispanic or Latino of any race were 6.4% of the population.