What is the largest city in Adams County, IL?

Quincy is the largest city or town in Adams County, with about 39,109 residents.

How many ZIP codes are in Adams County?

Adams County includes 16 ZIP Code Tabulation Areas, including 62301, 62305, 62320, 62324, 62325.

What is the population of Adams County, IL?

About 64,754 people live in Adams County, based on American Community Survey 5-year estimates.

What counties border Adams County?

Adams County borders Marion County, MO, Hancock County, Pike County, Lewis County, MO, Schuyler County, Brown County.

Adams County, IL: Cities, ZIP Codes & Local Data

Population

64,754

Land area

855sq mi

People per sq mi

76

ZIP codes

16

Adams County at a glance

Adams County is 67% less dense than Illinois as a whole.
Households here earn a median of $66,220 a year, 21% less than the Illinois figure of $83,390.
A typical owner-occupied home is valued at $162,600 (38% below Illinois) and median rent is $828 a month.
The biggest population centers are Quincy (39,109), Camp Point (1,230) and Mendon (1,167).

Local data for Adams County, IL

Counts from official public data

Housing and community stats

Adams County, IL, American Community Survey 2020-2024

Full profile

Median household income

$66,220

Poverty rate

12.8%

Median home value

$162,600

Prices +8.1% in a year

Median rent

$828/mo

Homeownership

72.1%

Bachelor's or higher

27.5%

Median age

41.4

Average commute

16.9 min

Largest reported origins and ancestries: German Americans (22,047), Irish Americans (6,457), Italian Americans (1,345).

Home values and rents Income, education and commute

Economy and federal money

Jobs, income, federal spending and pandemic loans

Details

Unemployment rate

2.9%

Aug 2026, -0.8 pts in a year

Average annual pay

$56,401

32,380 jobs, 2025

Income per person

$62,377

BEA, 2024

Federal spending

$467M

FY 2026, $7,102 per person

PPP loans

$163M

3,250 loans, 20,512 jobs reported

Campaign donations

$284K

Itemized, 2026 cycle

Economy Federal spending PPP loans

How people get to work

Adams County, IL, workers 16 and older. American Community Survey 5-year estimates

Drove alone79.5%
Carpooled8.3%
Public transit0.4%
Walked2.6%
Bicycle0.4%
Taxi, ride-hailing, motorcycle or other1.2%
Worked from home7.6%

Average one-way commute: 16.9 minutes for people who do not work from home.

Environment and hazard risk

Adams County, IL, from FEMA, NOAA and EPA

Full report

Natural hazard risk

Relatively Low

Top: heat wave

Storm events since 1996

520

Most often thunderstorm wind

Flood insurance policies

74

0.3% of homes, county

July high / Jan low

86° / 19°F

36.4 inches of rain a year

Hazards, floods and storm history Check a flood zone 18 historic places

Health statistics

Share of adults in Adams County, IL, CDC PLACES estimates

All 40 measures

Obesity

37.8%

U.S. 33.3% +4.5 pts

Diabetes

12.0%

U.S. 12.1% about the same

Smoking

14.4%

U.S. 12.8% +1.6 pts

Uninsured (18-64)

7.3%

U.S. 11.1% -3.8 pts

Cities, towns and ZIP codes in Adams County

Population shown

Frequently asked questions

What is the largest city in Adams County, IL?: Quincy is the largest city or town in Adams County, with about 39,109 residents.
How many ZIP codes are in Adams County?: Adams County includes 16 ZIP Code Tabulation Areas, including 62301, 62305, 62320, 62324, 62325.
What is the population of Adams County, IL?: About 64,754 people live in Adams County, based on American Community Survey 5-year estimates.
What counties border Adams County?: Adams County borders Marion County, MO, Hancock County, Pike County, Lewis County, MO, Schuyler County, Brown County.