What is the largest city in St. Clair County, MI?

Port Huron is the largest city or town in St. Clair County, with about 28,620 residents.

How many ZIP codes are in St. Clair County?

St. Clair County includes 21 ZIP Code Tabulation Areas, including 48001, 48002, 48006, 48014, 48022.

What is the population of St. Clair County, MI?

About 160,221 people live in St. Clair County, based on American Community Survey 5-year estimates.

What counties border St. Clair County?

St. Clair County borders Macomb County, Lapeer County, Sanilac County.

St. Clair County, MI: Cities, ZIP Codes & Local Data

Population

160,221

Land area

722sq mi

People per sq mi

222

ZIP codes

21

St. Clair County at a glance

St. Clair County is 25% denser than Michigan as a whole.
By population, it ranks 13th among 83 counties in Michigan.
The median household income is $71,270, close to the Michigan median.
A typical owner-occupied home is valued at $224,600 (3% below Michigan) and median rent is $1,029 a month.
Its largest cities are Port Huron (28,620), Marysville (9,925) and St. Clair (5,585).

Local data for St. Clair County, MI

Counts from official public data

Housing and community stats

St. Clair County, MI, American Community Survey 2020-2024

Full profile

Median household income

$71,270

Poverty rate

11.3%

Median home value

$224,600

Prices +4.8% in a year

Median rent

$1,029/mo

Homeownership

80.8%

Bachelor's or higher

20.3%

Median age

44.5

Average commute

28.5 min

Largest reported origins and ancestries: German Americans (40,997), Irish Americans (20,608), Polish Americans (18,312).

Home values and rents Income, education and commute

Economy and federal money

Jobs, income, federal spending and pandemic loans

Details

Unemployment rate

5.3%

Aug 2026, +0.9 pts in a year

Average annual pay

$58,073

41,734 jobs, 2025

Income per person

$57,943

BEA, 2024

Federal spending

$1.18B

FY 2026, $7,388 per person

PPP loans

$259M

2,985 loans, 32,421 jobs reported

Campaign donations

$580K

Itemized, 2026 cycle

Economy Federal spending PPP loans

How people get to work

St. Clair County, MI, workers 16 and older. American Community Survey 5-year estimates

Drove alone79.9%
Carpooled8.8%
Public transit1.1%
Walked1.1%
Bicycle0.4%
Taxi, ride-hailing, motorcycle or other0.9%
Worked from home7.7%

Average one-way commute: 28.5 minutes for people who do not work from home.

Environment and hazard risk

St. Clair County, MI, from FEMA, NOAA and EPA

Full report

Natural hazard risk

Relatively Moderate

Top: cold wave

Storm events since 1996

536

Most often thunderstorm wind

Flood insurance policies

1,248

2.0% of homes, county

July high / Jan low

83° / 16°F

35.9 inches of rain a year

Hazards, floods and storm history Check a flood zone 23 historic places

Health statistics

Share of adults in St. Clair County, MI, CDC PLACES estimates

All 40 measures

Obesity

36.5%

U.S. 33.3% +3.2 pts

Diabetes

12.2%

U.S. 12.1% about the same

Smoking

16.3%

U.S. 12.8% +3.5 pts

Uninsured (18-64)

6.7%

U.S. 11.1% -4.4 pts

Cities, towns and ZIP codes in St. Clair County

Population shown

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Frequently asked questions

What is the largest city in St. Clair County, MI?: Port Huron is the largest city or town in St. Clair County, with about 28,620 residents.
How many ZIP codes are in St. Clair County?: St. Clair County includes 21 ZIP Code Tabulation Areas, including 48001, 48002, 48006, 48014, 48022.
What is the population of St. Clair County, MI?: About 160,221 people live in St. Clair County, based on American Community Survey 5-year estimates.
What counties border St. Clair County?: St. Clair County borders Macomb County, Lapeer County, Sanilac County.