Alton is a city on the Mississippi River in Madison County, Illinois, United States, about 15 miles north of St. Louis, Missouri. The population was 27,865 at the 2010 census. It is a part of the Metro-East region of the Greater St. Louis metropolitan area. It is famous for its limestone bluffs along the river north of the city, for its role preceding and during the American Civil War, and as the hometown of jazz musician Miles Davis and Robert Wadlow, the tallest known person in history.