Hammond ( HAM-ənd) is a city in Lake County, Indiana, United States. It is part of the Chicago metropolitan area, and the only city in Indiana to border Chicago. First settled in the mid-19th century, it is one of the oldest cities of northern Lake County. As of the 2020 United States census, it is also the largest in population: the 2020 population was 77,879, 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. Notable local landmarks include the parkland around Wolf Lake and the Horseshoe Hammond riverboat casino. Part of the Rust Belt, Hammond has been industrial almost from its inception, but is also home to a Purdue University campus and numerous historic districts that showcase the residential and commercial architecture of the early 20th century.