Adams County, Illinois

Adams County is a county in Illinois, United States, about 93 miles north of St. Louis, Missouri, on the Mississippi River. It had a population of 65,737 at the 2020 census, an estimated 64,754 by 2024, and covers 871 square miles (2,260 km2) centred near 39°59′N 91°11′W.

Quincy is the county seat and its largest city; its postal code is 62301. The county holds 1 city, 13 incorporated villages and 6 unincorporated communities across 23 townships, and it runs on Central Time. Its FIPS code is 17001.

Towns & Villages in Adams County

Adams County has 20 named places on record: 1 city, 13 incorporated villages and 6 unincorporated communities with no local government of their own. CDP stands for census designated place; Unincorp. covers hamlets and rural crossroads with no formal boundary.

Golden and Columbus each straddle two townships, so their population figures above are village-wide totals, not per-township counts. Columbus shares its 62320 ZIP with the larger village of Camp Point several miles away rather than carrying its own. The county’s earlier place list also carried dozens of subdivision-style names — Cherry Lane Estates, Grandview Acres, Hillside Manor and similar — that have no independent Census or Wikipedia record; they are omitted here rather than guessed at.

Townships

Quincy Township is not listed separately — it is coextensive with the city of Quincy, so its population is counted in the city figure above rather than as a 23rd township row.

ZIP Codes

• 62301 — Quincy (the county’s main ZIP; the city also uses 62302 through 62306 for post office boxes and specific facilities)
• 62320 — Camp Point (also serves Columbus)
• 62324 — Clayton
• 62325 — Coatsburg
• 62339 — Golden
• 62346 — La Prairie
• 62347 — Liberty
• 62348 — Lima
• 62349 — Loraine
• 62351 — Mendon
• 62360 — Payson
• 62365 — Plainville
• 62376 — Ursa

Bigneck, Chatton, Kellerville, North Quincy, Spring Valley and Woodville have no ZIP code of their own; mail to these hamlets is delivered under a neighbouring incorporated town’s code.

Geography

Adams County sits in west-central Illinois on the east bank of the Mississippi River, which forms the county’s entire western border with Missouri. Of the county’s 871 square miles, 855 are land and 16 are water, about 1.9 percent, most of it the river itself and the smaller streams — Bear Creek, McKee Creek and Mill Creek among them — that drain into it. The terrain is rolling farmland typical of the Illinois prairie, cut by the river bluffs along its western edge.

Hancock County lies to the north, Schuyler County to the east, Pike County to the south, and Brown County borders the county’s southeastern corner. Across the Mississippi River to the west lie Marion County and Lewis County, both in Missouri. Hancock County, Schuyler County, Pike County, Marion County and Lewis County all border Adams directly; Brown County does not yet have its own page on this site.

Demographics

Adams County had a population of 65,737 at the 2020 census, and the latest Census Bureau estimate puts the county near 64,754 residents as of 2024, a slight decline. Quincy and Camp Point are the two largest communities, with Quincy alone holding well over half the county’s population. Median household income runs $66,220 (2024), below Illinois’s statewide figure of $80,306 (2023 ACS). Population density works out to roughly 77 people per square mile of land, concentrated heavily around Quincy and the townships that border it.

Economy & Local Life

Health care and social assistance employs the most workers in the county, about 5,953 people, followed by manufacturing at 4,457 and retail trade at 4,197. Blessing Hospital, Quincy Public Schools and manufacturer Titan rank among the area’s top employers. Quincy University, a Catholic liberal arts college founded in the 1860s, and John Wood Community College both sit in the county seat. Gardner Denver and GatesAir, both with roots in Quincy’s manufacturing history, remain part of the local industrial base. The county’s biggest annual event is Quincy’s Dogwood Parade and Festival each May, timed to the blooming of the city’s dogwood trees.

History

The Illinois General Assembly formed Adams County on 13 January 1825, carving it out of Pike County. It was named for John Quincy Adams, then serving as the sixth president of the United States. Quincy, founded in 1819 and incorporated as a city in 1870, grew fast enough on Mississippi River trade and German immigration to become Illinois’s second-largest city by 1870.

Quincy hosted the sixth of the seven Lincoln-Douglas debates on 13 October 1858, drawing a crowd estimated at 12,000 to Washington Park in the city’s centre. Abraham Lincoln and Stephen Douglas argued the extension of slavery into the territories two years before Lincoln’s election as president.

Getting There

Interstate 172 links Quincy to US 24 on the county’s north side. US Route 24 and US Route 36 cross the county through Quincy, along with Illinois Route 57, Illinois Route 61, Illinois Route 94, Illinois Route 96, Illinois Route 104 and Illinois Route 110.

• Hannibal, Missouri — about 17 miles south
• St. Louis, Missouri — about 93 miles south
• Chicago, Illinois — about 222 air miles north

Quincy Regional Airport, about 5 miles east of downtown Quincy, offers subsidized commercial flights and general aviation. Amtrak’s Illinois Zephyr and Carl Sandburg trains stop at the Quincy station, connecting to Chicago.

Frequently Asked Questions

Where is Adams County located?
It sits in west-central Illinois on the Mississippi River, about 93 miles north of St. Louis and directly across the river from Marion and Lewis counties in Missouri.

What is the population of Adams County?
65,737 at the 2020 census, with a 2024 estimate near 64,754.

How big is Adams County?
871 square miles (2,260 km2) in total, of which 855 square miles are land.

What is the county seat of Adams County?
Quincy, founded in 1819 and incorporated as a city in 1870, is the county seat and largest city.

How many towns and villages are in Adams County?
One city, Quincy, plus 13 incorporated villages — Camp Point, Payson, Mendon, Golden, Clayton, Ursa, Liberty, Loraine, Plainville, Coatsburg, Lima, Columbus and La Prairie — and 6 unincorporated communities: Bigneck, Chatton, Kellerville, North Quincy, Spring Valley and Woodville.

What ZIP codes does Adams County use?
62301 through 62306 for Quincy, plus a separate ZIP for each of the 13 incorporated villages, from 62320 (Camp Point and Columbus) to 62376 (Ursa).

What is Adams County known for?
Hosting the sixth Lincoln-Douglas debate in Quincy in 1858, and Quincy’s 19th-century growth into Illinois’s second-largest city on Mississippi River trade and German immigration.

More counties in this state: Towns and villages in Illinois.