Quincy, city, seat (1825) of Adams county, westernIllinois, U.S. It lies on theMississippi River, there bridged toMissouri, about 140 miles (225 km) northwest ofSt. Louis.Sauk,Fox, andKickapoo Indians were early inhabitants of the area.Jacques Marquette andLouis Jolliet stopped at what would become Quincy in 1673 during their exploration along the Mississippi River. The area was settled in 1822 by New Yorker John Wood (12th governor of Illinois, 1860–61). First known asBluffs, it became the county seat on March 4, 1825, the day that PresidentJohn Quincy Adams was inaugurated, and was renamed in Adams’s honour. During the winter of 1838–39, Mormons found refuge there before proceeding northward along the river toNauvoo. The city received an influx of German immigrants in the 1840s. Quincy grew rapidly as a river town with the increase in steamboat traffic in the 1850s and became an important shipping point and stop for travelers. Because of the city’s proximity to Missouri (a slave state), the issue ofslavery created much political controversy. Quincy was a part of theUnderground Railroad (a system by which slaves were assisted in escaping to the North and to Canada). The city declined with the passing of the steamboat era in the 1870s, but after 1920 industrial development stimulated its growth. Quincy’s economy is based on agriculture (including corn [maize], soybeans, and livestock) and manufacturing (including elevators, radio and television parts, air compressors, petroleum equipment, electronics, wheels, and truck bodies).

On October 13, 1858, Quincy’s Washington Park (originally John’s Square) was the site of the sixth of theLincoln-Douglas debates betweenAbraham Lincoln andStephen A. Douglas; before election to the U.S. Senate, Douglas represented the city in the U.S. House of Representatives. Quincy University was established in 1860, Gem City College in 1870, Blessing-Rieman College of Nursing in 1891, and John WoodCommunity College in 1974. Other institutions include Chaddock (a child services organization) and the Illinois Veterans Home (1886). Quinsippi Island Park, in the Mississippi River, has been developed as a recreation area. Historic buildings include the Governor John Wood Mansion (1835) and the Newcomb-Stillwell Mansion (1891; now home to the Quincy Museum). The city is the headquarters of theMark Twain National Wildlife Refuge Complex. Inc. town, 1834; city, 1840. Pop. (2000) 40,366; (2010) 40,633.