• county
  • FIPS 17133
  • Largest town: Waterloo

Monroe County, Illinois

Monroe County had 34,969 residents in the Census Vintage 2024 estimate, on 385.3 square miles of land. It ranks 40th of 102 in Illinois by population and 75th by land area.

Population
34,969
#40 of 102 in Illinois · #1,313 in US
Area
385.3 sq mi
#75 of 102 in Illinois · #2,583 in US
Density
91 / sq mi
#26 of 102 in Illinois · #984 in US
Median household income
$103,032
#5 of 102 in Illinois · #110 in US

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

Monroe County within Illinois. Pin: Springfield.

Measure from here

Tools and pages that start from Monroe County

Monroe County population, land area and income

Monroe County had 34,969 residents in the Census Vintage 2024 estimate, on 385.3 square miles of land. It ranks 40th of 102 in Illinois by population and 75th by land area. That works out to 90.8 people per square mile, near the US average of 96.3, and above the national county median.

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

Its SAIPE 2023 median household income of $103,032 is in the top tenth among 3,143 counties with an estimate.

National rank among 3,144

Population

34,969

3144th1st

1313th of 3,144 (US)

Land area

385 sq mi

3144th1st

2583rd of 3,144 (US)

Density

90.8 / sq mi

3144th1st

984th of 3,144 (US)

Median household income

$103,032

3143rd1st

110th of 3,143 (US)

Rank within Illinois (102)

Population

34,969

102nd1st

40th of 102 (IL)

Land area

385 sq mi

102nd1st

75th of 102 (IL)

Density

90.8 / sq mi

102nd1st

26th of 102 (IL)

Median household income

$103,032

102nd1st

5th of 102 (IL)

How Monroe County's population changed since 2020

Monroe County gained 16 residents between the July 2020 and July 2024 estimates, a rise of 0.0%. That ranks 14th 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, Monroe County recorded 1,104 births and 1,536 deaths, a natural change of -432. Net international migration added +2 and net domestic migration, people moving to or from other US counties, came to +450. The largest single component was domestic migration, which added 450 people.

35.0k202035.0k202135.1k202235.1k202335.0k2024
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
1,104
Deaths
1,536
Net international migration
+2
Net domestic migration
+450
Change, July 2023 to July 2024
-175

Where Monroe County is

The Census internal point of Monroe County is at 38.278000, -90.179100. It sits in UTM zone 15N. The map shades Illinois's 102 county-equivalents by population change from 2020 to 2024, darker for faster growth, with Monroe 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: Monroe County internal point. Dark pin: Springfield.

Internal point

Decimal
38.278000, -90.179100
DMS
38°16'40.80"N 90°10'44.76"W
UTM
15N 746753.0E 4240425.0N
Geohash
9yzcgbm9d
Plus code
86CF7RHC+59

Towns in Monroe County

3 incorporated places of 1,000+ people have residents in Monroe County, 23,104 people together, or 66% of the county. Each figure counts only the part of the town inside Monroe County; towns marked "part" extend into another county. The largest is Waterloo with 11,165.

  1. 01Waterloo11,165
  2. 02Columbia (part)10,725
  3. 03Valmeyer1,214
Census Vintage 2024 subcounty estimates, county parts of incorporated places (SUMLEV 157).

Counties bordering Monroe County

The Census 2024 county adjacency file lists 5 neighbors for Monroe County, including 3 across a state line. The most populous is St. Louis County, MO, with 992,929 residents. Distances run between Census internal points in a straight line.

Distance to Springfield and the nearest big city

Springfield is 107.7 miles NNE of Monroe County's internal point in a straight line. The nearest place of 100,000 or more is St. Louis, MO (population 279,695), 25.0 miles away. The nearest place of 10,000 or more is Waterloo, IL (population 11,165), 4.6 miles away.

Monroe County FIPS code

The FIPS code of Monroe County is 17133: state code 17 for Illinois plus county code 133. Use it as text, with the leading zero, when joining Census, BLS, or CDC county tables. SAIPE lists its 2023 median household income as $103,032.

Questions people ask

What is the population of Monroe County, Illinois?

The Census Vintage 2024 estimate for July 1, 2024 is 34,969. That is up 16 people (0.0%) from the July 2020 estimate of 34,953.

What is the FIPS code of Monroe County?

17133. The first two digits (17) are Illinois; the last three (133) identify the county.

What is the largest town in Monroe County?

Waterloo, with 11,165 residents inside Monroe County in 2024.

Which counties border Monroe County?

5 county-equivalents border it in the Census 2024 adjacency file: St. Louis County, MO; St. Clair County, IL; Jefferson County, MO; Randolph County, IL; Ste. Genevieve County, MO.

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.