Merrillville is a town in Ross Township, Lake County, Indiana, United States. The population was 35,246 at the 2010 census. Merrillville is in east-central Lake County, in the Chicago metropolitan area. On January 1, 2015, Merrillville became the most populated town in Indiana, as Fishers in Hamilton County was converted from a town to a city. The town serves as a major shopping hub for Northwest Indiana.