Seneca Township is located in McHenry County, Illinois. As of the 2020 census, its population was 2,893 and it contained 1,102 housing units. It includes the census-designated place of Franklinville.

Official town website ↗

From Wikipedia, licensed CC BY-SA 4.0 · facts via Wikidata (CC0)

How Seneca ranks

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#83Highest income in IL #71Best schools in IL #197Lowest obesity in IL All IL rankings →

Town numbers

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Living in Seneca

Health in Seneca

B⁺

Health Grade B+

Healthier than 73% of U.S. towns on seven CDC estimates.

Compared with Illinois

4better than IL·1worse

of 32 measures CDC estimates. The other 27 are too close to call.

Conditions 1▼ 11 close Habits all close Care all close Mind all close Everyday needs 4▲ 0 close

BetterToo close to callWorse

What stands out

12.6%Fewer adults facing food insecurityIL 15.9% · better 6.2%Fewer adults facing a utility shut-offIL 7.8% · better 8.8%More adults who have had cancerIL 7.6% · worse

Care nearby

Mercy Harvard HospitalHarvard · 10.2 mi · ER · rural critical access

Aunt Martha's Woodstock Community Health CenterWoodstock · 6.4 mi · sliding-scale fees

Primary careNo shortage

DentalNo shortage

Mental healthShortage · county-wide

CDC PLACES 2025 · modeled estimates for adults · ZIP codes 60098, 60152, 60180 · CMS · HRSAHealth in Seneca →

Natural hazards in Seneca

Moderate

Expected storm and flood damage is higher than in 41% of U.S. communities.

🌊 Inland flooding🌪️ Tornadoes🥶 Cold waves

3Does Seneca flood?paid flood claims since 2007 NoneDisasters that paid out hereof 14 declared for McHenry County MapSeneca vs. its neighborsnearby towns shaded by rating

FEMA National Risk Index December 2025 · OpenFEMANatural hazards in Seneca →

Schools in Seneca

All Seneca schools →

B⁺

School Grade B+

The public schools Seneca’s kids attend, from kindergarten through graduation, outperform 69% of Illinois’s districts on state tests and graduation. Among towns with similar incomes, they sit near the middle.

#71Best public schoolsof 384 in IL

DistrictMarengo CHSD 154Schools2

Westwood Elem School AElementary · Grades 1–5 · 385 students Marengo High School A-High · Grades 9–12 · 685 students

School data from the U.S. Department of Education (NCES, EDFacts). The School Grade is our own summary of state test results and graduation rates, graded within IL. Ratings are from neighbors.