Township · Illinois
Monmouth Township, Illinois
Monmouth Township, township, in Warren County, Illinois. Monmouth Township had 9,599 residents on July 1, 2025 by the Census Bureau's estimate, down 3.6% since 2020; the 2020 Census counted 9,975 and the ACS 2020-2024 5-year estimates put it at 9,727 (±27). GEOID 1718750023.
Residents, July 2025 estimate
9,599
Census Bureau estimate (no margin published)
2020 Census count: 9,975 · ACS 2020-2024: 9,727 ±27
Median household income
$61,897
±$5,166 (90% margin)
Illinois: $83,390
Median home value
$100,600
±$10,322 (90% margin)
Illinois: $263,300
Median gross rent
$733
±$68 (90% margin)
Illinois: $1,274
Where is Monmouth Township and what county is it in?
Monmouth Township is a township in Warren County, Illinois. It covers 36.8 square miles of land, 271 residents per square mile in 2020.
One place lies inside Monmouth Township: Monmouth (city, 8,902 in 2020).
Source: 2024 Gazetteer and 2020 place-by-county files, U.S. Census Bureau · Census reference files
How many people live in Monmouth Township, and is it growing?
The Census Bureau estimates that 9,599 people lived in Monmouth Township on July 1, 2025, down 3.6% since 2020, a steeper fall than Illinois's (−0.8%). The 2020 Census counted 9,975 residents. The 2020-2024 American Community Survey, a five-year sample, puts the population at 9,727 (±27).
| Measure | Monmouth Township | Warren County | Change since 2015-2019 |
|---|---|---|---|
| Total population | 9,727±27 | 16,447 | −349 |
| Households | 3,870±234 | 6,787 | no clear change |
| Average household size | 2.26±0.14 | 2.27 | no clear change |
| Housing units | 4,301±178 | 7,587 | no clear change |
Monmouth Township's population since 2000
From 10,799 in 2000 to 9,599 in 2025: down 11.1%. The 2000, 2010 and 2020 figures are census counts, each for Monmouth Township as it was drawn that year: a place that annexed land, or a community that has since incorporated, covered a different area then. The 2005 figure is the Census Bureau's intercensal estimate, revised to fit the 2000 and 2010 counts and drawn on 2010 boundaries; 2015 and 2025 are July 1 estimates made from the census before them.
Source: The 2000, 2010 and 2020 Census counts and the Census Bureau's population estimates (intercensal 2000-2010, Vintage 2020, Vintage 2025) · Census population estimates
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026); Census PEP Vintage 2025 (SUB-EST2025, CO-EST2025); 2020 Census P.L. 94-171 · Check it at data.census.gov
Who lives in Monmouth Township?
The median resident of Monmouth Township is 35.7 years old; 23.2% are under 18 and 18.9% are 65 or older. The largest group is non-Hispanic white residents at 72.3%, then Hispanic or Latino residents (of any race) at 16.7%. 9.8% of residents were born outside the United States.
| Measure | Monmouth Township | Warren County | Change since 2015-2019 |
|---|---|---|---|
| Median age | 35.7±1.4 | 38.5 | no clear change |
| Under 18 years | 23.2%±1.7 pts | 22.5% | – |
| 65 years and over | 18.9%±1.4 pts | 20.0% | – |
| Male | 48.7%±1.9 pts | 50.3% | – |
| Hispanic or Latino (any race) | 16.7%±1.2 pts | 11.1% | +1.4 pts |
| White alone, not Hispanic | 72.3%±1.9 pts | 81.1% | no clear change |
| Black or African American alone, not Hispanic | 3.9%±1.5 pts | 2.7% | no clear change |
| Asian alone, not Hispanic | 3.6%±0.9 pts | 2.4% | no clear change |
| American Indian and Alaska Native alone, not Hispanic | 0.2%±0.2 pts | 0.1% | – |
| Native Hawaiian and Other Pacific Islander alone, not Hispanic | 0.2%±0.3 pts | 0.1% | – |
| Two or more races, not Hispanic | 2.6%±1.4 pts | 2.1% | – |
| Some other race alone, not Hispanic | 0.4%±0.7 pts | 0.3% | – |
| Born outside the United States | 9.8%±1.6 pts | 6.5% | no clear change |
| Speak a language other than English at home (age 5+) | 17.0%±2.3 pts | 12.0% | – |
| Civilian veterans (age 18+) | 5.4%±1.6 pts | 7.3% | – |
| With a disability | 14.8%±2.4 pts | 13.8% | – |
| No health insurance coverage | 4.9%±2.2 pts | 5.0% | no clear change |
| High school graduate or higher (age 25+) | 84.1%±3.2 pts | 87.1% | – |
| Bachelor's degree or higher (age 25+) | 21.2%±3.6 pts | 22.0% | no clear change |
| Graduate or professional degree (age 25+) | 7.7%±2.2 pts | 7.9% | – |
| Lived in the same house a year earlier | 85.2%±3.5 pts | 87.6% | – |
| Moved from another state in the past year | 1.7%±1.0 pts | 1.4% | – |
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026) (Data Profiles DP02, DP05) · Check it at data.census.gov
What do households in Monmouth Township earn?
Half of Monmouth Township's 3,870 households earn less than $61,897 a year (±$5,166), against $67,385 in Warren County and $83,390 in Illinois. In 2015-2019 it was $54,507 in 2024 dollars; the margins of error cannot tell the two periods apart. 16.7% of residents live below the poverty line.
| Measure | Monmouth Township | Warren County | Change since 2015-2019 |
|---|---|---|---|
| Median household income | $61,897±$5,166 | $67,385 | no clear change |
| Mean household income | $81,648±$8,338 | $86,803 | – |
| Per capita income | $32,034±$3,168 | $35,164 | +$4,090 |
| People below the poverty line | 16.7%±4.0 pts | 14.6% | no clear change |
| Children under 18 below the poverty line | 31.3%±10.6 pts | 24.8% | no clear change |
| Households receiving SNAP | 20.6%±4.3 pts | 16.0% | – |
| Households with a computer | 92.4%±3.4 pts | 93.0% | – |
| Households with a broadband subscription | 85.1%±4.4 pts | 84.7% | – |
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026) (Data Profile DP03) · Check it at data.census.gov
What does housing cost in Monmouth Township?
Owners occupy 70.7% of Monmouth Township's occupied homes and renters 29.3%. The median owner-occupied home is valued at $100,600 by its owner (±$10,322). The median renter pays $733 a month including utilities, and 26.4% of renters pay 35% or more of their income on rent.
| Measure | Monmouth Township | Warren County | Change since 2015-2019 |
|---|---|---|---|
| Median home value (owner-occupied) | $100,600±$10,322 | $105,000 | no clear change |
| Median gross rent | $733±$68 | $788 | no clear change |
| Renters paying 35% or more of income on rent | 26.4%±11.0 pts | 26.5% | no clear change |
| Median monthly owner costs, with a mortgage | $1,011±$102 | $1,059 | – |
| Owner-occupied homes | 70.7%±4.7 pts | 75.2% | no clear change |
| Renter-occupied homes | 29.3%±4.7 pts | 24.8% | – |
| Housing units | 4,301±178 | 7,587 | no clear change |
| Homeowner vacancy rate | 0.9%±1.0 pts | 0.6% | – |
| Rental vacancy rate | 3.2%±5.0 pts | 3.3% | – |
| Single-family detached homes | 81.4%±4.2 pts | 87.3% | – |
| Mobile homes | 3.1%±2.0 pts | 2.6% | – |
| Built 2020 or later | 0.8%±1.1 pts | 0.5% | – |
| Built 2010 to 2019 | 0.6%±0.5 pts | 1.6% | – |
| Built 1939 or earlier | 33.0%±4.9 pts | 33.9% | – |
| Households with no vehicle | 9.4%±2.7 pts | 6.9% | – |
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026) (Data Profile DP04) · Check it at data.census.gov
How do people in Monmouth Township work and get to work?
76.1% of Monmouth Township's workers drive alone and 7.4% work from home. The average trip to work takes 15.4 minutes. The unemployment rate in 2020-2024 averaged 3.2%.
| Measure | Monmouth Township | Warren County | Change since 2015-2019 |
|---|---|---|---|
| In the labor force (age 16+) | 61.6%±3.6 pts | 61.0% | – |
| Unemployment rate | 3.2%±2.0 pts | 3.6% | −7.2 pts |
| Drove alone to work | 76.1%±4.6 pts | 80.5% | – |
| Carpooled | 7.1%±2.4 pts | 5.6% | – |
| Public transportation | 1.1%±1.2 pts | 0.7% | – |
| Walked | 6.5%±2.5 pts | 4.6% | – |
| Worked from home | 7.4%±2.3 pts | 7.4% | +4.4 pts |
| Mean travel time to work | 15.4 min±2.3 | 18.8 min | no clear change |
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026) (Data Profile DP03) · Check it at data.census.gov
What census tracts are in Monmouth Township?
2 census tracts lie mostly in Monmouth Township, and 2 more reach into it (2020 census blocks). Their median household incomes run from $61,225 (Tract 8704) to $63,345 (Tract 8705).
| Tract | Residents, 2020-2024 | Median household income |
|---|---|---|
| Tract 8705Warren County | 4,620 | $63,345 |
| Tract 8704Warren County | 4,600 | $61,225 |
| Tract 8703Warren County | 2,472 | $65,000 |
| Tract 8701Warren County | 2,446 | $83,902 |
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026); 2020 block assignment files (tract share = share of the tract's census blocks in Monmouth Township) · Census block assignment files
How does Monmouth Township compare with other places in Illinois?
By the Census Bureau's July 2025 estimates, Monmouth Township is the 1,277th-most populous of the 16,079 U.S. towns and townships that have one and the 154th-most populous of 1,407 in Illinois.
Monmouth Township ranks 1,048th of 1,380 places in Illinois with 1,000 or more residents and a reliable estimate, by median household income.
| Measure | Rank | Of |
|---|---|---|
| Population, July 2025 estimate | 154th | 1,407 |
| Growth 2020-2025 (PEP) | 1,151st | 1,347 |
| Residents per square mile | 854th | 1,383 |
| Median household income | 1,048th | 1,380 |
| Per capita income | 1,070th | 1,383 |
| Median home value | 1,176th | 1,379 |
| Median gross rent | 1,112th | 1,280 |
| Poverty rate | 219th | 1,119 |
| Bachelor's degree or higher | 818th | 1,369 |
| Median age | 1,224th | 1,383 |
| Owner-occupied share | 1,007th | 1,382 |
| Work from home | 806th | 1,015 |
| Travel time to work | 1,345th | 1,382 |
Monmouth Township's figures with every place in Illinois (CSV)
Every place in Illinois, sortable · Compare Monmouth Township with other places
Source: PlainCities ranks computed from the American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026) and PEP Vintage 2025 · How ranks are computed
How reliable are the figures for Monmouth Township?
8 of the 57 figures for Monmouth Township on this page carry a coefficient of variation over 40% and are marked with a ring: they come from a small sample, so read them as rough.
The American Community Survey samples about one household in eight over five years, so every figure is an estimate with a 90% margin of error (shown under each value). A ring marks an estimate whose coefficient of variation is over 40%. A change is called only when the gap between the two periods is larger than their combined 90% margin (the square root of the sum of the two squared margins), the Census Bureau's test. How to read a margin of error.
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026): margins of error as published · ACS technical documentation
How these figures are made: methodology and release checks · reading a margin of error · every state · corrections
Not on this page: crime, weather and schools for Monmouth Township are other agencies' records. Crime: the FBI's Crime Data Explorer · climate: NOAA's U.S. Climate Normals · schools: the National Center for Education Statistics' school search.