Quincy, known as the "Gem City", is a city on the Mississippi River and county seat of Adams County, Illinois, United States. As of the 2000 census the city had 40,366 people. The community is a river city and was built on top of the bluffs. Quincy serves as the economic and cultural hub of West-Central Illinois and is the primary city of the Quincy, IL–MO Micropolitan Statistical Area.