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.

Northwest Indiana, nicknamed The Region after the Calumet Region, is an unofficial region of northern Indiana, United States that is located at the northwestern corner of the state. Though there is no official definition of the region, it is based on the Gary, Indiana Metropolitan Division, which comprises Jasper, Lake, Porter and Newton counties in Indiana, and the Michigan City-La Porte, IN Metropolitan Statistic Area, which comprises LaPorte, with unofficial definitions also including Starke and Pulaski counties. This region neighbors Lake Michigan and parts of it are in the Chicago metropolitan area. According to the 2020 Census, the largest definition of Northwest Indiana has a population of 866,965 and is the state's second largest urban area after the Indianapolis Metropolitan Area. It is also the home of the Indiana Dunes, parts of which have been preserved through conservation efforts. The town of Ogden Dunes houses the Hour Glass, a museum showcasing the ecological and conservation efforts of O. D. Frank.