Afton is a city in Washington County, Minnesota, United States. The population was 2,886 at the 2010 United States Census. It lies on a small bay where Valley Creek empties into the St. Croix River, several miles north of its confluence with the Mississippi River. Afton is well known for Afton Alps, the largest ski and snowboard area in the Twin Cities metropolitan area. It is home to Afton State Park on the St. Croix River.