Half of Seneca Township’s homes were built after 1986
More historic than 20% of U.S. towns · #637 of 768 in Illinois. What drives it
Most of Seneca Township was built recently: 5% of its homes predate 1940 and the median home dates from 1986. Below: maps from 1932 on and old-book passages.
On its age, its old homes and the National Register, Seneca Township is more historic than 20% of U.S. towns, #637 of 768 in Illinois. Its share of homes from before 1940 holds the grade up; its National Register listings pull it down.
C−
HistoryA character grade: shown, never part of Seneca Township’s overall grade.
Few Illinois towns list much on the Register (a typical Illinois town has 0.5 per 10,000 residents, the U.S. 2.4), so Seneca Township’s 0.0 sits below most of its state (28% of Illinois towns have fewer) while its 0 listings outnumber those of 23% of U.S. towns.
How sure. Graded on two of the three inputs, so a change in either one moves the letter more than it would with three. The pre-1940 share is a Census survey estimate (±5.3 points).
Founding year: our sources. Homes: Census ACS 2020–24. National Register: National Park Service, May 2026 list; each listing counted once (boundary changes and added documentation belong to their listing), and a historic district counts its contributing buildings. How TownRatings grades history →
What stands out about Seneca Township’s past
Read from the archive, the National Register and the record. The page puts what stands out first.
Wikipedia doesn’t have a history of Seneca Township yet. The photos, dates and memories neighbors add here are how it gets written.
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.
Its population held steady between the last two censuses: 2,944 in 2010, 2,893 in 2020.
Intro from Wikipedia. Population: U.S. Census Bureau.
From the old history books
What they wrote about Seneca Township in 1922
Passages that mention Seneca Township, cut from the printed page as they were published.
In Seneca Township the first school was taught by Mrs. Roxy Stevens in 1840. at her home which was one mile south of Franklinville. In Franklinville the first schoolhouse of the township, a frame building, was erected in 1S45.
Text read by machine from the scan; it may contain errors.
History of McHenry County, Illinois1922 · page 340Read the page →
Read the text
At the Deitz school house in Seneca Township, school was in session. and about eighteen scholars and the teacher, Mary E. Goodrich, were present. The house standing directly in the track of the storm was taken from its foundation and carried several feet, turned half around and torn to pieces leaving only the front end of the building standing.
Text read by machine from the scan; it may contain errors.
Scans and text from the Internet Archive. Books published in 1930 or earlier, which are in the public domain.
By decade
No old photos in the archives yet
Weddings on Main Street, storms, parades, school pictures, the old store. If it’s in your family album, it belongs here.
Be the first to add onePhotograph a print flat, in daylight, no flash.
Every edition of the U.S. Geological Survey’s map of Seneca Township. Tap a year, or press play to watch the town change.
1932Harvard sheet · 1:62,500
U.S. Geological Survey historical topographic maps (public domain), via Esri’s collection of the scans. The red ring marks the center of Seneca Township.
Famous people
Famous people close to Seneca Township
Nobody well known was born in Seneca Township itself, so here are the best known from just nearby.
Seneca Township is more historic than 20% of U.S. towns, #637 of 768 in Illinois. The History grade combines the town’s founding era, the share of homes built before 1940 and its National Register listings. It’s a character grade, so it isn’t part of the overall grade. How it works.
How old are the homes in Seneca Township?
5% of Seneca Township’s homes were built before 1940 (Census estimate, ±5.3 points), against a typical 11% for an Illinois town; the median home was built in 1986.
Founding dates: Wikidata, Wikipedia, the U.S. post office records of Blevins & Helbock (CC0) and the Census. Homes by year built: Census ACS 2020–24. National Register of Historic Places: National Park Service (list of May 22, 2026). Old photos, postcards and papers: Wikimedia Commons, the Library of Congress and other public archives, credited on each item’s page. Maps: U.S. Geological Survey historical topographic maps (via Esri) and Sanborn fire-insurance maps (Library of Congress). History text and census tables: Wikipedia (CC BY-SA 4.0). Places that used to be: USGS Geographic Names Information System (2021).
From U.S. Geological Survey historical maps, the USGS Geographic Names Information System and old county and town histories (Internet Archive). Archive images are copied here with their credits and licenses, shown on each photo’s page. Refreshed monthly.
