what county is quincy illinois
Quincy, IL. Sponsored Topics. Quincy, known as Illinois' Gem City, is a river city along the Mississippi River and the county seat of Adams County. As of the 2010 census the city held a population of 40,633. The city anchors its own micropolitan area and is the economic and regional hub of West-central Illinois, catering a trade area of well over 300,000.