How old are the homes in Seneca Township, IL?

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

40.8% (±16.9 points) of the homes in Seneca Township, IL were built before 1980 (2020–2024 American Community Survey).

5.4% were built before 1940.

6.9% were built in 2010 or later.

Figures last updated on November 12, 2026.

Built before 1980: 40.8% (±16.9 points)
Built before 1940: 5.4%
Built 2010 or later: 6.9%

When the homes in Seneca Township were built

Housing units by year structure built, 2020–2024
Year built	Seneca Township	McHenry County	Illinois	United States
2020 or later	0.0% (±3.2 points)	1.1%	0.7%	2.0%
2010 to 2019	6.9% (±9.2 points)	4.4%	5.0%	9.4%
2000 to 2009	24.3% (±10.1 points)	20.1%	11.2%	13.6%
1990 to 1999	12.1% (±7.9 points)	22.6%	10.5%	12.4%
1980 to 1989	15.8% (±11.9 points)	13.4%	9.2%	12.9%
1970 to 1979	25.2% (±11.0 points)	13.6%	14.2%	14.2%
1960 to 1969	0.0% (±3.2 points)	6.5%	11.5%	9.9%
1950 to 1959	0.8% (±1.3 points)	7.3%	11.9%	9.5%
1940 to 1949	9.4% (±11.3 points)	3.0%	5.6%	4.4%
1939 or earlier	5.4% (±4.9 points)	8.0%	20.2%	11.7%

In Seneca Township, the share of homes built before 1980 is not measurably different from McHenry County (38.4%).

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

It is not measurably different from the national figure (49.7%).

In McHenry County, Seneca Township ranks 28 of 46 places with a published estimate, from highest to lowest share of homes built before 1980.

Statewide, it ranks 2408 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 (15.6%) and the share built before 1980 (40.8%).

Homes built before 1980 in places near Seneca Township

Nearest places with a published estimate, compared with Seneca Township
Place	Distance	Homes built before 1980	Compared with this place
Seneca Township	—	40.8% (±16.9 points)	—
Union	4.2 mi	83.0% (±21.0 points)	Higher
Woodstock	4.8 mi	38.9% (±4.7 points)	Not measurably different
Marengo	4.8 mi	54.5% (±11.5 points)	Not measurably different
Hartland Township	5.5 mi	46.9% (±20.2 points)	Not measurably different
Dorr Township	5.7 mi	45.6% (±5.5 points)	Not measurably different
Marengo Township	6.0 mi	57.3% (±11.3 points)	Not measurably different
Coral Township	6.6 mi	47.0% (±14.8 points)	Not measurably different
Dunham Township	8.3 mi	47.7% (±22.3 points)	Not measurably different

Nearby places with a measurably higher figure: Union, IL (83.0%).

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

Homes built before 1980 across McHenry County, place by place

Rank	Place	Homes built before 1980
22	Dorr Township	45.6% (±5.5 points)
23	Bull Valley	44.1% (±14.4 points)
24	Algonquin Township	42.0% (±2.5 points)
25	Ringwood	41.8% (±10.5 points)
26	Crystal Lake	41.5% (±3.5 points)
27	Greenwood Township (McHenry County)	40.9% (±6.7 points)
28	Seneca Township	40.8% (±16.9 points)
29	Woodstock	38.9% (±4.7 points)
30	Cary	38.8% (±5.9 points)
31	McHenry	38.6% (±4.0 points)
32	Riley Township	37.3% (±16.0 points)
33	Nunda Township	34.1% (±3.1 points)
34	Island Lake	29.8% (±6.4 points)

Showing 13 of 46 places in McHenry 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 Seneca Township

How old are most homes in Seneca Township?

40.8% of homes in Seneca Township, IL were built before 1980 (2020–2024 American Community Survey).

Do homes in Seneca 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 15.6% and 40.8% of homes in Seneca Township were built before then.

Does a contractor need lead certification to work on older homes in Seneca 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 — Seneca township, McHenry 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 Seneca township, McHenry County, Illinois (county subdivision:68653, in state:17 county:111).

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.