Rock Island is a city in and the
county seat of
Rock Island County, Illinois, United States. The original Rock Island, from which the city name is derived, is the largest island on the Mississippi River. It is now called
Arsenal Island. The population was 39,018 at the
2010 census. Located on the
Mississippi River, it is one of the
Quad Cities, along with neighboring
Moline,
East Moline, and the
Iowa cities of
Davenport and
Bettendorf. The Quad Cities has a population of about 380,000. The city is home to
Rock Island Arsenal, the largest government-owned weapons manufacturing
arsenal in the US, which employs 6,000 people.