where is collinsville il
Collinsville, Illinois. Collinsville is a city located mainly in Madison County, and partially in St. Clair County, both in Illinois. As of the 2010 census, the city had a population of 25,579, an increase from 24,707 in 2000. Collinsville is approximately 12 miles from St. Louis, Missouri and is considered part of that city's Metro-East area.