• county
  • FIPS 17199
  • Largest town: Marion

Williamson County, Illinois

Williamson County had 67,064 residents in the Census Vintage 2024 estimate, on 420.2 square miles of land. It ranks 22nd of 102 in Illinois by population and 68th by land area.

Population
67,064
#22 of 102 in Illinois · #815 in US
Area
420.2 sq mi
#68 of 102 in Illinois · #2,412 in US
Density
160 / sq mi
#19 of 102 in Illinois · #670 in US
Median household income
$60,704
#77 of 102 in Illinois · #1,767 in US

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

Williamson County within Illinois. Pin: Springfield.

Measure from here

Tools and pages that start from Williamson County

Williamson County population, land area and income

Williamson County had 67,064 residents in the Census Vintage 2024 estimate, on 420.2 square miles of land. It ranks 22nd of 102 in Illinois by population and 68th by land area. That works out to 159.6 people per square mile, 1.7 times the US average of 96.3, and in the top quarter nationally.

The median county-equivalent in Illinois has 24,447 residents, so Williamson County is 2.7 times that size.

Its SAIPE 2023 median household income of $60,704 is below the national county median among 3,143 counties with an estimate.

National rank among 3,144

Population

67,064

3144th1st

815th of 3,144 (US)

Land area

420 sq mi

3144th1st

2412th of 3,144 (US)

Density

159.6 / sq mi

3144th1st

670th of 3,144 (US)

Median household income

$60,704

3143rd1st

1767th of 3,143 (US)

Rank within Illinois (102)

Population

67,064

102nd1st

22nd of 102 (IL)

Land area

420 sq mi

102nd1st

68th of 102 (IL)

Density

159.6 / sq mi

102nd1st

19th of 102 (IL)

Median household income

$60,704

102nd1st

77th of 102 (IL)

How Williamson County's population changed since 2020

Williamson County lost 57 residents between the July 2020 and July 2024 estimates, a drop of 0.1%. That ranks 18th 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, Williamson County recorded 2,645 births and 3,703 deaths, a natural change of -1,058. Net international migration added +363 and net domestic migration, people moving to or from other US counties, came to +565. The largest single component was natural change, which removed 1,058 people.

67.1k202066.9k202166.6k202266.7k202367.1k2024
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
2,645
Deaths
3,703
Net international migration
+363
Net domestic migration
+565
Change, July 2023 to July 2024
+327

Where Williamson County is

The Census internal point of Williamson County is at 37.730400, -88.930000. 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 Williamson 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: Williamson County internal point. Dark pin: Springfield.

Internal point

Decimal
37.730400, -88.930000
DMS
37°43'49.44"N 88°55'48.00"W
UTM
16N 329924.5E 4177656.3N
Geohash
dn8y8ke5s
Plus code
869HP3JC+52

Towns in Williamson County

6 incorporated places of 1,000+ people have residents in Williamson County, 41,690 people together, or 62% of the county. Each figure counts only the part of the town inside Williamson County; towns marked "part" extend into another county. The largest is Marion with 17,021.

  1. 01Marion17,021
  2. 02Herrin12,253
  3. 03Carterville5,821
  4. 04Johnston City3,309
  5. 05Cambria1,793
  6. 06Crainville1,493
Census Vintage 2024 subcounty estimates, county parts of incorporated places (SUMLEV 157).

Counties bordering Williamson County

The Census 2024 county adjacency file lists 5 neighbors for Williamson County. The most populous is Jackson County, IL, with 53,199 residents. Distances run between Census internal points in a straight line.

Distance to Springfield and the nearest big city

Springfield is 146.9 miles NNW of Williamson County's internal point in a straight line. The nearest place of 100,000 or more is Evansville, IN (population 115,395), 78.2 miles away. The nearest place of 10,000 or more is Marion, IL (population 17,021), 0.7 miles away.

Williamson County FIPS code

The FIPS code of Williamson County is 17199: state code 17 for Illinois plus county code 199. Use it as text, with the leading zero, when joining Census, BLS, or CDC county tables. SAIPE lists its 2023 median household income as $60,704.

Questions people ask

What is the population of Williamson County, Illinois?

The Census Vintage 2024 estimate for July 1, 2024 is 67,064. That is down 57 people (0.1%) from the July 2020 estimate of 67,121.

What is the FIPS code of Williamson County?

17199. The first two digits (17) are Illinois; the last three (199) identify the county.

What is the largest town in Williamson County?

Marion, with 17,021 residents inside Williamson County in 2024.

Which counties border Williamson County?

5 county-equivalents border it in the Census 2024 adjacency file: Jackson County, IL; Franklin County, IL; Saline County, IL; Union County, IL; Johnson 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.