Plymouth is a city in Hennepin County in the U.S. state of Minnesota. A suburb in the Minneapolis–Saint Paul metropolitan area, the city is ab…Plymouth is a city in Hennepin County in the U.S. state of Minnesota. A suburb in the Minneapolis–Saint Paul metropolitan area, the city is about 10 miles west of downtown Minneapolis. The population was 81,026 at the 2020 census, making it Minnesota's 7th-largest city.