What is the largest city in Jefferson County, MO?

Arnold is the largest city or town in Jefferson County, with about 20,956 residents.

How many ZIP codes are in Jefferson County?

Jefferson County includes 16 ZIP Code Tabulation Areas, including 63010, 63012, 63016, 63019, 63020.

What is the population of Jefferson County, MO?

About 229,458 people live in Jefferson County, based on American Community Survey 5-year estimates.

What counties border Jefferson County?

Jefferson County borders St. Louis County, Franklin County, St. Francois County, Monroe County, IL, Washington County, Ste. Genevieve County.

Jefferson County, MO: Cities, ZIP Codes & Local Data

Population

229,458

Land area

656sq mi

People per sq mi

350

ZIP codes

16

Jefferson County at a glance

Jefferson County is about 3.9 times as dense as Missouri as a whole.
It is the 7th most populous of 115 counties in Missouri.
Households here earn a median of $82,851 a year, 17% more than the Missouri figure of $70,702.
A typical owner-occupied home is valued at $237,200 and median rent is $979 a month.
The biggest population centers are Arnold (20,956), Festus (13,201) and Murphy (8,285).

Local data for Jefferson County, MO

Counts from official public data

Housing and community stats

Jefferson County, MO, American Community Survey 2020-2024

Full profile

Median household income

$82,851

Poverty rate

9.0%

Median home value

$237,200

Prices +4.0% in a year

Median rent

$979/mo

Homeownership

82.2%

Bachelor's or higher

24.7%

Median age

40.3

Average commute

30.6 min

Largest reported origins and ancestries: German Americans (67,083), Irish Americans (33,468), Italian Americans (12,077).

Home values and rents Income, education and commute

Economy and federal money

Jobs, income, federal spending and pandemic loans

Details

Unemployment rate

3.0%

Sep 2026, -0.2 pts in a year

Average annual pay

$52,302

49,584 jobs, 2025

Income per person

$56,907

BEA, 2024

Federal spending

$1.4B

FY 2026, $6,386 per person

PPP loans

$463M

5,234 loans, 49,314 jobs reported

Campaign donations

$667K

Itemized, 2026 cycle

Economy Federal spending PPP loans

How people get to work

Jefferson County, MO, workers 16 and older. American Community Survey 5-year estimates

Drove alone79.5%
Carpooled7.2%
Public transit0.1%
Walked0.6%
Bicycle0.0%
Taxi, ride-hailing, motorcycle or other0.9%
Worked from home11.5%

Average one-way commute: 30.6 minutes for people who do not work from home.

Environment and hazard risk

Jefferson County, MO, from FEMA, NOAA and EPA

Full report

Natural hazard risk

Relatively Moderate

Top: strong wind

Storm events since 1996

664

Most often hail

Flood insurance policies

591

0.7% of homes, county

July high / Jan low

88° / 22°F

43.6 inches of rain a year

Hazards, floods and storm history Check a flood zone 6 historic places

Health statistics

Share of adults in Jefferson County, MO, CDC PLACES estimates

All 40 measures

Obesity

40.3%

U.S. 33.3% +7.0 pts

Diabetes

11.2%

U.S. 12.1% -0.9 pts

Smoking

16.5%

U.S. 12.8% +3.7 pts

Uninsured (18-64)

7.9%

U.S. 11.1% -3.2 pts

Cities, towns and ZIP codes in Jefferson County

Population shown

Frequently asked questions

What is the largest city in Jefferson County, MO?: Arnold is the largest city or town in Jefferson County, with about 20,956 residents.
How many ZIP codes are in Jefferson County?: Jefferson County includes 16 ZIP Code Tabulation Areas, including 63010, 63012, 63016, 63019, 63020.
What is the population of Jefferson County, MO?: About 229,458 people live in Jefferson County, based on American Community Survey 5-year estimates.
What counties border Jefferson County?: Jefferson County borders St. Louis County, Franklin County, St. Francois County, Monroe County, IL, Washington County, Ste. Genevieve County.