QUINCY, a town of the United States of North America, capital of Adams county, in the state of Illinois, stands on a limestone cliff on the left bank of the Mississippi, in the midst of a rich undulating prairie-land, 170 miles above St Louis, and 104 W. of Springfield. It has a large public square, numerous churches, a handsome court-house, several newspaper offices, and three banks. There are numerous manufactories, including distilleries, machine shops, foundries, flour and saw mills worked by steam, &c. An active trade is carried on by steamers on the Mississippi. Pop. (1850) 6901; (1853) 11,000.