Formed January 1, 1825 (34th county)

Adams County (65,727), Quincy (39,473)
The red brick courthouse was built in 1950 and sits on Vermont Street at 5th Street, one block east of United States Highway 24. The Modern style architecture was provided by Holabird, Root, & Burgee and Hafner & Hafner. The building was renovated in 1997. The building features marble walls inside. The county was organized on January 1, 1825 out of Pike County as the 34th county. There were 1837 and 1877 courthouses also in Quincy, the only county seat. The county and county seat are named for President John Quincy Adams.
Adams County government consists of a sheriff, an attorney, a coroner, a clerk, a treasurer, and an assessor (executive). It has 7 Board Members (legislative.) Thirteen Circuit Court Judges serve Adams, Brown, Calhoun, Cass, Mason, Menard, Pike, and Schuyler counties and a court clerk serves Adams County (judicial.) Adams County is in western Illinois on the border with Missouri. Saint Louis, Missouri is southeast and Springfield, Illinois is directly east of the county. The Mississippi River forms the western border of the county. The county center is 9.2 miles East-Northeast of Quincy nearer Fowler. The county is surrounded clockwise by Hancock, Brown, Schuyler, and Pike counties and Missouri.
The area of the county is 855 square miles. It is 12 out of 102 in the state. It ranks 23 out of 102 in population in the state. It has a density of 76.9 persons per square mile making it 32 out of 102 in the state. Adams County has 69.9% of its population in its incorporated areas. Interstate Highway 172 originates in the county and heads south into Pike County. United States Highway 24 enters the county from the east, Brown County, and heads west into Missouri. The county is rectangular except for the wandering Mississippi River on its western border. Quincy is located on the western border. Quincy is the county seat and the largest city. It is 60.1% of the county population. This county is in the Quincy Micropolitan Statistical Area.

Camp Point
Clayton
Coatsburg
Columbus
Golden
La Prairie
Liberty
Lima
Loraine
Mendon
Payson
Plainville
Quincy
Ursa

