Monmouth, Illinois demographics

Monmouth, IL demographics: median age 34.1; 18.3% of adults 25+ hold a bachelor’s degree. Age, race, households, languages and education, ACS 2020–2024 with margins of error.

ACS 2020–2024 · Monmouth city, Illinois · Incorporated city · GEOID 1750010. The survey estimates a population of 8,581 for its five-year window. This is separate from the annual July 2025 population estimate on the city overview.

Median age in Monmouth is 34.1 years, with a 90% margin of error of 1.5 years. There are 3,323 households (±258). Age and household distributions show how these totals are composed; they do not establish which neighborhood suits a particular person.

Every count and share is an estimate. “±” is a 90% margin of error (MOE); pp means percentage points. Derived shares use the category count divided by the named universe. Aggregated category MOEs and percentage MOEs are approximate. A margin larger than half its estimate is flagged as low precision. Blank source uncertainty is shown as unavailable, never zero.

Age distribution and sex

City, state and U.S. estimates · ACS 2020–2024
Measure / survey universe	City estimate ± MOE	State estimate ± MOE	U.S. estimate ± MOE
Median age Total population · years	34.1 ±1.5	39.0 ±0.1	38.9 ±0.1

Age groups · B01001 · ACS 2020–2024 Total population: 8,581
Category	Count ± MOE	Share ± MOE (pp)	Illinois	U.S.
Under 18	2,040 ±273	23.8% ±3.1 pp	21.8%	22.0%
18–34	2,355 ±271	27.4% ±3.0 pp	22.7%	22.8%
35–64	2,825 ±300	32.9% ±3.3 pp	38.5%	38.0%
65 and older	1,361 ±234	15.9% ±2.7 pp	17.0%	17.2%

Sex categories as published by ACS · B01001 · ACS 2020–2024 Total population: 8,581
Category	Count ± MOE	Share ± MOE (pp)	Illinois	U.S.
Male	4,143 ±205	48.3% ±1.8 pp	49.4%	49.5%
Female	4,438 ±265	51.7% ±2.6 pp	50.6%	50.5%

The age groups are mutually exclusive and cover the entire population. The sex categories follow this ACS table’s published classification; they are not a survey of gender identity.

Race and Hispanic origin

Race · B02001 · ACS 2020–2024 Total population: 8,581
Category	Count ± MOE	Share ± MOE (pp)	Illinois	U.S.
White alone	6,321 ±382	73.7% ±3.7 pp	61.0%	61.0%
Black or African American alone	383 ±142	4.5% ±1.6 pp	13.6%	12.2%
American Indian and Alaska Native alone	153 ±117 · low precision	1.8% ±1.4 pp · low precision	0.6%	0.9%
Asian alone	355 ±88	4.1% ±1.0 pp	6.0%	6.0%
Native Hawaiian and Other Pacific Islander alone	70 ±95 · low precision	0.8% ±1.1 pp · low precision	0.0%	0.2%
Some other race alone	765 ±230	8.9% ±2.7 pp	7.9%	7.1%
Two or more races	534 ±219	6.2% ±2.5 pp	10.9%	12.6%

Hispanic or Latino origin · B03003 · ACS 2020–2024 Total population: 8,581
Category	Count ± MOE	Share ± MOE (pp)	Illinois	U.S.
Not Hispanic or Latino	7,032 ±285	81.9% ±1.9 pp	81.2%	80.7%
Hispanic or Latino	1,549 ±123	18.1% ±1.3 pp	18.8%	19.3%

Hispanic origin and race are separate questions. People of Hispanic or Latino origin may be of any race and appear in both tables. Do not add the Hispanic share to race shares. Race alone and two-or-more-race groups are the mutually exclusive categories of the race table.

Household types, children and living alone

Household types · B11001 · ACS 2020–2024 Households: 3,323
Category	Count ± MOE	Share ± MOE (pp)	Illinois	U.S.
Married-couple family	1,156 ±161	34.8% ±4.0 pp	45.3%	46.9%
Other family: male householder, no spouse present	317 ±99	9.5% ±2.9 pp	4.9%	5.1%
Other family: female householder, no spouse present	607 ±176	18.3% ±5.1 pp	11.9%	12.2%
Nonfamily: householder living alone	1,110 ±204	33.4% ±5.6 pp	31.2%	28.7%
Nonfamily: householder not living alone	133 ±88 · low precision	4.0% ±2.6 pp · low precision	6.7%	7.0%

Households with children · B11005 · ACS 2020–2024 Households: 3,323
Category	Count ± MOE	Share ± MOE (pp)	Illinois	U.S.
Households with people under 18	959 ±154	28.9% ±4.1 pp	28.6%	29.5%
Households without people under 18	2,364 ±261	71.1% ±5.6 pp	71.4%	70.5%

Household size · B11016 · ACS 2020–2024 Households: 3,323
Category	Count ± MOE	Share ± MOE (pp)	Illinois	U.S.
One-person nonfamily households	1,110 ±204	33.4% ±5.6 pp	31.2%	28.7%
Two-person households	1,017 ±199	30.6% ±5.5 pp	32.3%	33.8%
Three-person households	425 ±159	12.8% ±4.7 pp	14.7%	15.3%
Four-person households	442 ±107	13.3% ±3.0 pp	12.6%	12.6%
Five-person households	211 ±116 · low precision	6.3% ±3.5 pp · low precision	5.8%	5.9%
Six-person households	60 ±51 · low precision	1.8% ±1.5 pp · low precision	2.1%	2.2%
Seven or more people	58 ±44 · low precision	1.7% ±1.3 pp · low precision	1.3%	1.4%

A family household contains related people under the Census definition. A nonfamily household can contain one person or unrelated people sharing a home. Households with children can also appear in the household-type and size tables, so those tables must not be added together. Household estimates exclude people living in group quarters from the household universe.

Nativity and languages spoken at home

Nativity · B05002 · ACS 2020–2024 Total population: 8,581
Category	Count ± MOE	Share ± MOE (pp)	Illinois	U.S.
Native	7,683 ±335	89.5% ±2.5 pp	85.3%	85.9%
Foreign born	898 ±159	10.5% ±1.8 pp	14.7%	14.1%

Language spoken at home · C16001 · ACS 2020–2024 Population age 5 and older: 8,145
Category	Count ± MOE	Share ± MOE (pp)	Illinois	U.S.
English only	6,647 ±349	81.6% ±3.3 pp	76.0%	77.7%
Spanish	898 ±172	11.0% ±2.1 pp	14.0%	13.6%
French, Haitian, or Cajun	128 ±82 · low precision	1.6% ±1.0 pp · low precision	0.3%	0.7%
German or other West Germanic	0 ±18 · low precision	0.0% ±0.2 pp · low precision	0.3%	0.5%
Russian, Polish, or other Slavic	0 ±18 · low precision	0.0% ±0.2 pp · low precision	2.5%	0.7%
Other Indo-European	1 ±3 · low precision	0.0% ±0.0 pp · low precision	2.6%	2.0%
Korean	0 ±18 · low precision	0.0% ±0.2 pp · low precision	0.3%	0.3%
Chinese, including Mandarin and Cantonese	60 ±84 · low precision	0.7% ±1.0 pp · low precision	0.9%	1.1%
Vietnamese	0 ±18 · low precision	0.0% ±0.2 pp · low precision	0.2%	0.5%
Tagalog, including Filipino	10 ±15 · low precision	0.1% ±0.2 pp · low precision	0.7%	0.6%
Other Asian and Pacific Island	276 ±105	3.4% ±1.3 pp	1.0%	1.1%
Arabic	17 ±25 · low precision	0.2% ±0.3 pp · low precision	0.6%	0.5%
Other and unspecified	108 ±130 · low precision	1.3% ±1.6 pp · low precision	0.6%	0.8%

Foreign born means not a U.S. citizen at birth; it includes naturalized citizens. Language categories describe speech at home among people age five and older. A language other than English at home does not establish that someone cannot speak English. This city page uses the published C16001 summary categories because the more detailed B16001 table does not provide these city records in this release.

Educational attainment

Highest completed education · B15003 · ACS 2020–2024 Population age 25 and older: 5,056
Category	Count ± MOE	Share ± MOE (pp)	Illinois	U.S.
Less than high school graduate	810 ±200	16.0% ±3.9 pp	9.5%	10.4%
High school graduate or equivalency	1,797 ±278	35.5% ±5.3 pp	25.1%	26.0%
Some college, no degree	1,058 ±212	20.9% ±4.1 pp	19.2%	19.1%
Associate’s degree	467 ±121	9.2% ±2.4 pp	8.3%	8.8%
Bachelor’s degree	574 ±152	11.4% ±3.0 pp	22.6%	21.6%
Graduate or professional degree	350 ±102	6.9% ±2.0 pp	15.3%	14.1%

The denominator excludes residents under 25. Each person is counted in the highest attainment category they completed. This table does not measure the quality of local schools or the education level of every current student.

Residence one year earlier

Geographic mobility · B07003 · ACS 2020–2024 Population age 1 and older: 8,530
Category	Count ± MOE	Share ± MOE (pp)	Illinois	U.S.
Same house	7,115 ±401	83.4% ±3.8 pp	88.9%	87.7%
Moved within same county	830 ±268	9.7% ±3.1 pp	6.4%	6.3%
Moved from a different county in the same state	417 ±196	4.9% ±2.3 pp	2.4%	3.1%
Moved from a different state	168 ±100 · low precision	2.0% ±1.2 pp · low precision	1.6%	2.3%
Moved from abroad	0 ±18 · low precision	0.0% ±0.2 pp · low precision	0.6%	0.6%

These are respondents’ residence patterns one year before their survey response, pooled across the five-year window. They are not a net migration count for 2025. A person can move to a different house within the same city or county; moves within the same county should not automatically be interpreted as new arrivals to the city.

Health insurance, internet access and veterans

5.5% of Monmouth residents (±2.4 percentage points) had no health insurance coverage when surveyed, compared with 6.9% in Illinois and 8.4% nationally. 85.6% of households subscribe to broadband of any type, including cellular data plans. A subscription is not the same as available service: the FCC National Broadband Map shows providers at a specific address.

City, state and U.S. shares · ACS 2020–2024
Measure	Monmouth	Illinois	U.S.	Compared with Illinois
People without health insurance Civilian noninstitutionalized population	5.5% ±2.4 pp	6.9%	8.4%	Not statistically different
Households with a broadband subscription Households	85.6% ±3.1 pp	90.8%	91.0%	Lower
Veterans Civilian population age 18 and older	5.1% ±1.7 pp	4.8%	6.2%	Not statistically different

Reading and reusing the estimates

The Census table links above lead to the original detailed tables. Counts, source universes and uncertainty are retained in the source observation download for Monmouth . Compare these figures with the same survey window; do not compare one city’s five-year estimate with another city’s annual estimate as though they measured the same period. For methods, see uncertainty and denominator calculations.

Read Monmouth housing and cost context or return to the city profile.