Carlinville is a city in Macoupin County, Illinois, United States.As of the 2010 Census, the population was 5,917, and 5,665 at a 2015 estimate. It is the county seat of Macoupin County, and is an outlying part of the Metro-East region of the Greater St. Louis metropolitan area.Carlinville is also the home of Blackburn College, a small college affiliated with the Presbyterian church, and Prairie Farms Dairy.