• county
  • FIPS 17121
  • Largest town: Centralia

Marion County, Illinois

Marion County had 36,437 residents in the Census Vintage 2024 estimate, on 572.5 square miles of land. It ranks 37th of 102 in Illinois by population and 40th by land area.

Population
36,437
#37 of 102 in Illinois · #1,284 in US
Area
572.5 sq mi
#40 of 102 in Illinois · #1,748 in US
Density
64 / sq mi
#37 of 102 in Illinois · #1,260 in US
Median household income
$54,774
#94 of 102 in Illinois · #2,342 in US

Census Vintage 2024 estimates · SAIPE 2023 income · 2024 Gazetteer land area

Marion County within Illinois. Pin: Springfield.

Measure from here

Tools and pages that start from Marion County

Marion County population, land area and income

Marion County had 36,437 residents in the Census Vintage 2024 estimate, on 572.5 square miles of land. It ranks 37th of 102 in Illinois by population and 40th by land area. That works out to 63.6 people per square mile, below the US average of 96.3, and above the national county median.

The median county-equivalent in Illinois has 24,447 residents; Marion County is somewhat larger.

Its SAIPE 2023 median household income of $54,774 is below the national county median among 3,143 counties with an estimate.

National rank among 3,144

Population

36,437

3144th1st

1284th of 3,144 (US)

Land area

573 sq mi

3144th1st

1748th of 3,144 (US)

Density

63.6 / sq mi

3144th1st

1260th of 3,144 (US)

Median household income

$54,774

3143rd1st

2342nd of 3,143 (US)

Rank within Illinois (102)

Population

36,437

102nd1st

37th of 102 (IL)

Land area

573 sq mi

102nd1st

40th of 102 (IL)

Density

63.6 / sq mi

102nd1st

37th of 102 (IL)

Median household income

$54,774

102nd1st

94th of 102 (IL)

How Marion County's population changed since 2020

Marion County lost 1,220 residents between the July 2020 and July 2024 estimates, a drop of 3.2%. That ranks 86th of 102 in Illinois for growth. The median Illinois county changed by -1.7%, and the state as a whole by -0.7%.

Since the April 2020 estimates base, Marion County recorded 1,830 births and 2,522 deaths, a natural change of -692. Net international migration added +35 and net domestic migration, people moving to or from other US counties, came to -649. The largest single component was natural change, which removed 692 people.

37.7k202037.4k202136.9k202236.6k202336.4k2024
Census Vintage 2024 county estimates for July 1 of each year. The axis starts above zero so year-to-year changes are visible.

Components of change, April 2020 to July 2024

Births
1,830
Deaths
2,522
Net international migration
+35
Net domestic migration
-649
Change, July 2023 to July 2024
-203

Where Marion County is

The Census internal point of Marion County is at 38.648200, -88.920400. It sits in UTM zone 16N. The map shades Illinois's 102 county-equivalents by population change from 2020 to 2024, darker for faster growth, with Marion County outlined. Dots are towns of 1,000+ people with residents in it.

Piatt County: -0.3%Hamilton County: -2.2%Williamson County: -0.1%Edgar County: -2.4%Macoupin County: -2.3%Marshall County: -1.3%Putnam County: +0.0%Richland County: -2.8%Washington County: -1.4%Lee County: -1.5%Douglas County: +0.2%Cook County: -1.6%Effingham County: -0.3%Edwards County: -3.6%Cass County: -2.0%Clay County: -3.4%Knox County: -2.2%LaSalle County: -0.9%Cumberland County: -1.3%Warren County: -3.7%Moultrie County: -0.9%Menard County: -2.5%Fayette County: -1.5%Boone County: -0.0%Lawrence County: -3.2%Marion County: -3.2%Champaign County: +3.0%Clark County: -2.4%Ford County: -0.4%Wayne County: -1.4%Logan County: -1.4%Grundy County: +2.5%Jasper County: -1.8%Crawford County: -1.3%McDonough County: -1.7%Clinton County: +0.5%Perry County: -3.0%Montgomery County: -2.2%Henry County: -2.0%Livingston County: -1.2%Scott County: -3.8%Alexander County: -11.2%Bureau County: -2.2%Brown County: +1.1%Mason County: -3.9%Calhoun County: -4.1%Greene County: -4.3%Coles County: -1.4%Kendall County: +8.2%Lake County: +0.7%Mercer County: -2.2%St. Clair County: -2.3%Wabash County: -3.0%Bond County: -1.7%DuPage County: +0.6%Gallatin County: -5.2%Stephenson County: -3.3%McHenry County: +1.9%White County: -3.0%Saline County: -3.9%Christian County: -2.2%Sangamon County: -1.0%Massac County: -3.6%Macon County: -2.9%Johnson County: -0.0%Jo Daviess County: -2.6%Peoria County: -1.0%DeKalb County: +1.0%Pope County: -1.5%De Witt County: -0.9%Schuyler County: -1.7%Fulton County: -3.1%Ogle County: -0.8%Jersey County: -1.6%Iroquois County: -3.3%Kankakee County: -0.9%Rock Island County: -1.1%Pulaski County: -5.8%Kane County: +0.9%Union County: -2.4%Whiteside County: -1.7%Woodford County: -0.3%Carroll County: -1.5%Adams County: -2.3%Hardin County: -2.6%Madison County: -1.0%Hancock County: -3.1%Monroe County: +0.0%Tazewell County: -1.1%Jackson County: -0.1%Vermilion County: -3.9%Randolph County: -0.6%McLean County: +0.5%Morgan County: -2.6%Shelby County: -1.7%Will County: +1.7%Winnebago County: -0.4%Jefferson County: -2.4%Stark County: -2.2%Henderson County: -4.5%Pike County: -2.6%Franklin County: -1.8%
Change 2020 to 2024
  1. < -3.0%
  2. < -2.2%
  3. < -1.4%
  4. < -0.3%
  5. ≥ -0.3%
no data

Orange pin: Marion County internal point. Dark pin: Springfield.

Internal point

Decimal
38.648200, -88.920400
DMS
38°38'53.52"N 88°55'13.44"W
UTM
16N 332881.9E 4279487.6N
Geohash
dnbgbednh
Plus code
86CHJ3XH+7R

Towns in Marion County

4 incorporated places of 1,000+ people have residents in Marion County, 18,845 people together, or 52% of the county. Each figure counts only the part of the town inside Marion County; towns marked "part" extend into another county. The largest is Centralia with 9,637.

  1. 01Centralia (part)9,637
  2. 02Salem7,016
  3. 03Sandoval1,125
  4. 04Central City1,067
Census Vintage 2024 subcounty estimates, county parts of incorporated places (SUMLEV 157).

Counties bordering Marion County

The Census 2024 county adjacency file lists 6 neighbors for Marion County. The most populous is Clinton County, IL, with 37,087 residents. Distances run between Census internal points in a straight line.

Distance to Springfield and the nearest big city

Springfield is 87.5 miles NNW of Marion County's internal point in a straight line. The nearest place of 100,000 or more is St. Louis, MO (population 279,695), 71.5 miles away. The nearest place of 10,000 or more is Centralia, IL (population 11,787), 14.0 miles away.

Marion County FIPS code

The FIPS code of Marion County is 17121: state code 17 for Illinois plus county code 121. Use it as text, with the leading zero, when joining Census, BLS, or CDC county tables. SAIPE lists its 2023 median household income as $54,774.

Questions people ask

What is the population of Marion County, Illinois?

The Census Vintage 2024 estimate for July 1, 2024 is 36,437. That is down 1,220 people (3.2%) from the July 2020 estimate of 37,657.

What is the FIPS code of Marion County?

17121. The first two digits (17) are Illinois; the last three (121) identify the county.

What is the largest town in Marion County?

Centralia, with 9,637 residents inside Marion County in 2024 (11,787 across all 3 counties it spans).

Which counties border Marion County?

6 county-equivalents border it in the Census 2024 adjacency file: Clinton County, IL; Jefferson County, IL; Fayette County, IL; Wayne County, IL; Washington County, IL; Clay County, IL.

Sources and data as of

Data as of: Census Vintage 2024 population estimates, 2024 Gazetteer land area and internal points, SAIPE 2023 median household income.

  1. 01Census Vintage 2024 county population estimates
  2. 02Census 2024 Gazetteer, counties
  3. 03Census SAIPE 2023 state and county estimates
  4. 04Census Vintage 2024 subcounty population estimates
  5. 05Census 2024 county adjacency file
  6. 06Census 2024 cartographic boundary file, counties (1:5,000,000)

How every number is computed: methodology. Spotted a wrong figure? Report an error.