City · Illinois
Waterloo, Illinois
Waterloo, city, in Monroe County, Illinois. Waterloo had 11,132 residents on July 1, 2025 by the Census Bureau's estimate, up 1.2% since 2020; the 2020 Census counted 11,013 and the ACS 2020-2024 5-year estimates put it at 11,129 (±38). GEOID 1779150.
Residents, July 2025 estimate
11,132
Census Bureau estimate (no margin published)
2020 Census count: 11,013 · ACS 2020-2024: 11,129 ±38
Median household income
$98,711
±$12,639 (90% margin)
Illinois: $83,390
Median home value
$249,500
±$17,511 (90% margin)
Illinois: $263,300
Median gross rent
$886
±$118 (90% margin)
Illinois: $1,274
Where is Waterloo and what county is it in?
Waterloo is a city in Monroe County, Illinois. It covers 8.3 square miles of land, 1,329 residents per square mile in 2020.
Waterloo is in the St. Louis, MO-IL metropolitan statistical area, which takes in 15 counties (Census Bureau delineation, July 2023).
Source: 2024 Gazetteer and 2020 place-by-county files, U.S. Census Bureau · Census reference files
How many people live in Waterloo, and is it growing?
The Census Bureau estimates that 11,132 people lived in Waterloo on July 1, 2025, up 1.2% since 2020, while Illinois shrank 0.8%. The 2020 Census counted 11,013 residents. The 2020-2024 American Community Survey, a five-year sample, puts the population at 11,129 (±38).
| Measure | Waterloo | Monroe County | Change since 2015-2019 |
|---|---|---|---|
| Total population | 11,129 ±38 | 35,036 | +762 |
| Households | 4,491 ±227 | 13,851 | no clear change |
| Average household size | 2.43 ±0.12 | 2.51 | no clear change |
| Housing units | 4,818 ±232 | 14,759 | +412 |
Waterloo's population since 2000
From 7,614 in 2000 to 11,132 in 2025: up 46.2%. The 2000, 2010 and 2020 figures are census counts, each for Waterloo 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 Waterloo?
The median resident of Waterloo is 41.5 years old; 21.9% are under 18 and 20.6% are 65 or older. The largest group is non-Hispanic white residents at 94.1%, then Hispanic or Latino residents (of any race) at 1.8%. 2.7% of residents were born outside the United States.
| Measure | Waterloo | Monroe County | Change since 2015-2019 |
|---|---|---|---|
| Median age | 41.5 ±2.6 | 43.2 | no clear change |
| Under 18 years | 21.9% ±2.0 pts | 21.8% | – |
| 65 years and over | 20.6% ±2.6 pts | 19.7% | – |
| Male | 48.8% ±1.9 pts | 50.2% | – |
| Hispanic or Latino (any race) | 1.8% ±1.5 pts | 1.9% | – |
| White alone, not Hispanic | 94.1% ±2.0 pts | 95.0% | no clear change |
| Black or African American alone, not Hispanic | 1.0% ±0.6 pts | 0.6% | – |
| Asian alone, not Hispanic | 1.7% ±0.6 pts | 0.6% | – |
| American Indian and Alaska Native alone, not Hispanic | 0.1% ±0.2 pts | 0.1% | – |
| Native Hawaiian and Other Pacific Islander alone, not Hispanic | 0.0% ±0.3 pts | 0.0% | – |
| Two or more races, not Hispanic | 1.3% ±0.8 pts | 1.6% | – |
| Some other race alone, not Hispanic | 0.0% ±0.3 pts | 0.2% | – |
| Born outside the United States | 2.7% ±1.1 pts | 1.2% | – |
| Speak a language other than English at home (age 5+) | 2.6% ±1.2 pts | 2.1% | – |
| Civilian veterans (age 18+) | 8.8% ±2.7 pts | 8.7% | – |
| With a disability | 12.5% ±2.5 pts | 10.6% | – |
| No health insurance coverage | 3.4% ±1.1 pts | 2.5% | no clear change |
| High school graduate or higher (age 25+) | 96.7% ±1.6 pts | 96.0% | – |
| Bachelor's degree or higher (age 25+) | 37.3% ±3.8 pts | 38.7% | +6.0 pts |
| Graduate or professional degree (age 25+) | 13.8% ±2.7 pts | 13.7% | – |
| Lived in the same house a year earlier | 91.1% ±2.3 pts | 92.6% | – |
| Moved from another state in the past year | 1.1% ±0.9 pts | 0.9% | – |
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 Waterloo earn?
Half of Waterloo's 4,491 households earn less than $98,711 a year (±$12,639), against $102,880 in Monroe County and $83,390 in Illinois. In 2015-2019 the median was $83,296 in 2024 dollars, so it rose by $15,415 after inflation. 5.9% of residents live below the poverty line.
| Measure | Waterloo | Monroe County | Change since 2015-2019 |
|---|---|---|---|
| Median household income | $98,711 ±$12,639 | $102,880 | +$15,415 |
| Mean household income | $116,241 ±$10,634 | $123,402 | – |
| Per capita income | $47,421 ±$3,857 | $49,605 | +$5,222 |
| People below the poverty line | 5.9% ±2.0 pts | 5.0% | no clear change |
| Children under 18 below the poverty line | 5.1% ±4.1 pts | 5.2% | – |
| Households receiving SNAP | 6.1% ±2.8 pts | 4.4% | – |
| Households with a computer | 96.1% ±1.9 pts | 94.7% | – |
| Households with a broadband subscription | 94.6% ±2.4 pts | 92.7% | – |
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 Waterloo?
Owners occupy 78.2% of Waterloo's occupied homes and renters 21.8%. The median owner-occupied home is valued at $249,500 by its owner (±$17,511). The median renter pays $886 a month including utilities, and 42.4% of renters pay 35% or more of their income on rent.
| Measure | Waterloo | Monroe County | Change since 2015-2019 |
|---|---|---|---|
| Median home value (owner-occupied) | $249,500 ±$17,511 | $282,100 | no clear change |
| Median gross rent | $886 ±$118 | $1,042 | no clear change |
| Renters paying 35% or more of income on rent | 42.4% ±12.9 pts | 39.5% | no clear change |
| Median monthly owner costs, with a mortgage | $1,835 ±$172 | $1,973 | – |
| Owner-occupied homes | 78.2% ±4.3 pts | 84.7% | no clear change |
| Renter-occupied homes | 21.8% ±4.3 pts | 15.3% | – |
| Housing units | 4,818 ±232 | 14,759 | +412 |
| Homeowner vacancy rate | 1.3% ±1.6 pts | 0.9% | – |
| Rental vacancy rate | 4.5% ±6.9 pts | 3.4% | – |
| Single-family detached homes | 77.8% ±4.3 pts | 83.5% | – |
| Mobile homes | 0.0% ±0.8 pts | 1.9% | – |
| Built 2020 or later | 0.4% ±0.6 pts | 1.3% | – |
| Built 2010 to 2019 | 15.1% ±4.3 pts | 11.1% | – |
| Built 1939 or earlier | 10.5% ±3.6 pts | 9.8% | – |
| Households with no vehicle | 6.3% ±2.9 pts | 4.0% | – |
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 many new homes is Waterloo building?
Builders took permits for 36 new housing units in Waterloo in 2025 (34 in single-family houses), 3.2 per 1,000 residents against 1.5 across Illinois.
Counts of units in permits a local office issued; not every permitted unit is built. A year marked with months was reported for part of the year.
Source: Building Permits Survey, annual place files 2019-2025, U.S. Census Bureau · Census Building Permits Survey
How do people in Waterloo work and get to work?
77.4% of Waterloo's workers drive alone and 12.9% work from home. The average trip to work takes 26.8 minutes.
| Measure | Waterloo | Monroe County | Change since 2015-2019 |
|---|---|---|---|
| In the labor force (age 16+) | 66.4% ±3.2 pts | 68.3% | – |
| Unemployment rate | 2.3% ±1.9 pts | 1.9% | – |
| Drove alone to work | 77.4% ±4.8 pts | 79.7% | – |
| Carpooled | 7.9% ±3.0 pts | 5.7% | – |
| Public transportation | 0.0% ±0.2 pts | 0.0% | – |
| Walked | 1.2% ±1.2 pts | 1.5% | – |
| Worked from home | 12.9% ±4.3 pts | 12.6% | no clear change |
| Mean travel time to work | 26.8 min ±2.0 | 28.3 min | −3.6 min |
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 Waterloo?
1 census tract lies mostly in Waterloo, and 2 more reach into it (2020 census blocks).
| Tract | Residents, 2020-2024 | Median household income |
|---|---|---|
| Tract 6004.01Monroe County | 7,761 | $100,845 |
| Tract 6005.01Monroe County | 6,568 | $101,972 |
| Tract 6004.02Monroe County | 4,867 | $96,613 |
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 Waterloo) · Census block assignment files
How does Waterloo compare with other places in Illinois?
By the Census Bureau's July 2025 estimates, Waterloo is the 2,981st-most populous of the 19,476 U.S. incorporated places that have one and the 207th-most populous of 1,294 in Illinois.
Waterloo ranks 361st 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 | 207th | 1,294 |
| Growth 2020-2025 (PEP) | 172nd | 1,347 |
| Residents per square mile | 503rd | 1,383 |
| Median household income | 361st | 1,380 |
| Per capita income | 328th | 1,383 |
| Median home value | 379th | 1,379 |
| Median gross rent | 772nd | 1,280 |
| Poverty rate | 900th | 1,119 |
| Bachelor's degree or higher | 308th | 1,369 |
| Median age | 637th | 1,383 |
| Owner-occupied share | 670th | 1,382 |
| Work from home | 388th | 1,015 |
| Travel time to work | 577th | 1,382 |
Waterloo's figures with every place in Illinois (CSV)
Every place in Illinois, sortable · Compare Waterloo 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 Waterloo?
13 of the 57 figures for Waterloo 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 Waterloo 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' public schools in Waterloo.