Merrillville /ˈmɛrəlvɪl/ is a town in Ross Township, Lake County, Indiana. The population was 35,246 at the 2010 census. Merrillville is located in the east-central portion of 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.