- Cottage Grove is a city 10 miles (16 km) south of Saint Paul in Washington County in the State of Minnesota. It lies on the north bank of the Mississippi River, north of the confluence with the St. Croix River. Cottage Grove and nearby suburbs form the southeast portion of Minneapolis-Saint Paul, the 16th-largest metropolitan area in the United States, with about 3.69 million residents. Its population was 38,839 at the 2020 census.