Hammond is a city in Lake County, Indiana, United States. It is part of the Chicago metropolitan area. First settled in the mid-19th century, it is one of the oldest cities of northern Lake County. As of the 2010 United States census, it is also the largest in population: the 2010 population was 80,830, replacing Gary as the most populous city in Lake County. From north to south, Hammond runs from Lake Michigan down to the Little Calumet River; from east to west along its southern border, it runs from the Illinois state line to Cline Avenue. The city is traversed by numerous railroads and expressways, including the South Shore Line, Borman Expressway, and Indiana Toll Road.