How old are the homes in Monmouth Township, IL?

Name: Age of homes in Monmouth Township, IL, 2020–2024
Creator: US Census Bureau
License: https://www.census.gov/data/developers/about/terms-of-service.html

84.2% (±8.4 points) of the homes in Monmouth Township, IL were built before 1980 (2020–2024 American Community Survey).

33.0% were built before 1940.

1.4% were built in 2010 or later.

Figures last updated on November 12, 2026.

Built before 1980: 84.2% (±8.4 points)
Built before 1940: 33.0%
Built 2010 or later: 1.4%

When the homes in Monmouth Township were built

Housing units by year structure built, 2020–2024
Year built	Monmouth Township	Warren County	Illinois	United States
2020 or later	0.8% (±1.1 points)	0.5%	0.7%	2.0%
2010 to 2019	0.6% (±0.5 points)	1.6%	5.0%	9.4%
2000 to 2009	6.3% (±2.7 points)	5.2%	11.2%	13.6%
1990 to 1999	3.7% (±1.9 points)	3.3%	10.5%	12.4%
1980 to 1989	4.3% (±2.1 points)	5.0%	9.2%	12.9%
1970 to 1979	13.0% (±3.2 points)	15.7%	14.2%	14.2%
1960 to 1969	14.5% (±3.4 points)	13.1%	11.5%	9.9%
1950 to 1959	15.4% (±3.8 points)	14.1%	11.9%	9.5%
1940 to 1949	8.3% (±3.2 points)	7.6%	5.6%	4.4%
1939 or earlier	33.0% (±4.9 points)	33.9%	20.2%	11.7%

In Monmouth Township, the share of homes built before 1980 is not measurably different from Warren County (84.4%).

It is also higher than in Illinois (63.4%).

It is higher than the national figure (49.7%).

In Warren County, Monmouth Township ranks 15 of 20 places with a published estimate, from highest to lowest share of homes built before 1980.

Statewide, it ranks 478 of 2,751.

Rankings use the estimates alone; where margins of error overlap, neighboring ranks may not truly differ.

Why the age of a home matters: lead-based paint

Federal law treats housing built before 1978 as likely to contain lead-based paint.

Before a lease or sale of most pre-1978 housing, the landlord or seller must disclose any known lead-based paint and hazards and give the tenant or buyer the EPA pamphlet (42 U.S.C. § 4852d; 40 CFR part 745, subpart F; 24 CFR part 35, subpart A).

A contractor paid to renovate, repair or paint a pre-1978 home must be a certified firm, use a certified renovator and follow lead-safe work practices under the Renovation, Repair and Painting Rule (40 CFR part 745, subpart E) whenever the job disturbs more than 6 square feet of painted surface in a room or more than 20 square feet outside; window replacement and demolition always count (40 CFR 745.83).

Certification comes from EPA, or from the state where EPA has authorized the state to run the program.

The Census Bureau groups construction by decade, so the share built before 1978 lies between the share built before 1970 (71.2%) and the share built before 1980 (84.2%).

Homes built before 1980 in places near Monmouth Township

Nearest places with a published estimate, compared with Monmouth Township
Place	Distance	Homes built before 1980	Compared with this place
Monmouth Township	—	84.2% (±8.4 points)	—
Monmouth	2.1 mi	88.1% (±9.2 points)	Not measurably different
Lenox Township	5.7 mi	100.0% (±74.0 points)	Not measurably different
Coldbrook Township	5.8 mi	100.0% (±49.5 points)	Not measurably different
Spring Grove Township	5.9 mi	80.0% (±16.6 points)	Not measurably different
Hale Township	6.7 mi	93.6% (±56.3 points)	Not measurably different
Tompkins Township	7.9 mi	86.8% (±17.2 points)	Not measurably different
Kelly Township	8.2 mi	80.3% (±35.7 points)	Not measurably different
Floyd Township	8.2 mi	100.0% (±36.1 points)	Not measurably different

None of the nearby places differs measurably from this one on this figure.

Distance is measured in a straight line between the Census Bureau’s internal points for each place.

Homes built before 1980 across Warren County, place by place

Rank	Place	Homes built before 1980
9	Kirkwood	90.8% (±19.1 points)
10	Little York	89.3% (±23.5 points)
11	Monmouth	88.1% (±9.2 points)
12	Swan Township	87.6% (±85.0 points)
13	Roseville	87.5% (±15.7 points)
14	Tompkins Township	86.8% (±17.2 points)
15	Monmouth Township	84.2% (±8.4 points)
16	Roseville Township	83.9% (±14.5 points)
17	Kelly Township	80.3% (±35.7 points)
18	Spring Grove Township	80.0% (±16.6 points)
19	Ellison Township	78.1% (±39.8 points)
20	Greenbush Township	49.3% (±19.8 points)

Showing 12 of 20 places in Warren County, ranked from highest to lowest.

Survey years: 2020–2024 (American Community Survey 5-year estimates).

Margins of error are at the 90% confidence level.

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Questions about Monmouth Township

How old are most homes in Monmouth Township?

84.2% of homes in Monmouth Township, IL were built before 1980 (2020–2024 American Community Survey).

Do homes in Monmouth Township need a lead paint disclosure?

A home built before 1978 does, before it is rented or sold, unless an exemption applies (42 U.S.C. § 4852d); between 71.2% and 84.2% of homes in Monmouth Township were built before then.

Does a contractor need lead certification to work on older homes in Monmouth Township?

Yes, when the job disturbs more than 6 square feet of paint in a room or 20 square feet outside, or replaces a window: the firm must be certified and a certified renovator must direct the work under the Renovation, Repair and Painting Rule (40 CFR part 745, subpart E).

Sources

Selected Housing Characteristics (DP04), 2020–2024 ACS 5-year estimates — Monmouth township, Warren County, Illinois

To check these figures in the Census Bureau’s own API, request the variables below from the 2024 ACS 5-year data profile (acs/acs5/profile) for Monmouth township, Warren County, Illinois (county subdivision:50023, in state:17 county:187).

Each estimate (E or PE) has a margin of error beside it (M or PM).

The API needs a free key.

Request a Census API key.

DP04_0017PE, DP04_0017PM, DP04_0018PE, DP04_0018PM, DP04_0019PE, DP04_0019PM, DP04_0020PE, DP04_0020PM, DP04_0021PE, DP04_0021PM, DP04_0022PE, DP04_0022PM, DP04_0023PE, DP04_0023PM, DP04_0024PE, DP04_0024PM, DP04_0025PE, DP04_0025PM, DP04_0026PE, DP04_0026PM

This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau.

Figures are published by the US Census Bureau, HUD, the Bureau of Labor Statistics and the FBI; Seayora reproduces them and does not adjust them, except where a sentence says it compares dollar figures after inflation. They describe the whole place, not any one building or street, and are not an appraisal, a rent determination, a tax bill, a safety rating or legal advice.