() is a city in Lake County, Indiana, United States. It is part of the Chicago metropolitan area. The population was 83,048 at the 2000 census.
According to the United States Census Bureau, the city has a total area of 24.8 square miles (64.3 km²), of which, 22.9 square miles (59.3 km²) of it is land and 2.0 square miles (5.1 km²) of it (7.85%) is water. The city's elevation above sea level is 176 m – 186 m (577 ft – 610 ft). The city sits within the boundaries of the former Lake Chicago. Most of the city is on sandy soil with a layer of black topsoil that varies from non-existent to several feet (a meter or more) thick. Much of the exposed sand has been removed for purposes such as industrial use to make concrete and glass.