The story
Read it all →How Illiopolis Township came to be
From Wikipedia’s history of Illiopolis Township.
The name was formed from Illinois and -polis, a Greek suffix meaning "city".
Text from Wikipedia, licensed CC BY-SA 4.0.
C+History
History · Illiopolis Township
Illiopolis Township’s post office opened in 1867, and 20% of its homes were built before 1940
More historic than 41% of U.S. towns. What drives it
Below: 1 old photo or paper, maps from 1954 on, and the census since 1870.
1867first post office
0on the National Register
20%homes built before 1940
1old photo or paper
Quick answers
How Illiopolis Township began
When was Illiopolis Township founded?
1867
The Illiopolis Township post office opened in 1867, the earliest record of the town by name.
First census: 395 in 18702020 census: 1,212159 years
How historic is Illiopolis Township?
C+
What drives the grade ↓More historic than 41% of U.S. towns, on its age, its old homes and the National Register.
Founding year: the first Illiopolis Township post office (Blevins & Helbock, CC0).The full story ↓
History grade
What drives Illiopolis Township’s History grade
On its age, its old homes and the National Register, Illiopolis Township is more historic than 41% of U.S. towns. 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 Illiopolis Township’s overall grade.
Founding era1867, from the first post office: founded 1850–1899, an older era than 37% of U.S. townsC+Homes built before 194020.3% of homes (±5.6) · typical IL town 10.6% · U.S. 8.4%B+National RegisterNo listings counted · typical IL town 0.5 per 10,000 · U.S. 2.4C
All U.S. towns we grade (21,289)Ahead of 41%
NewerOlder
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 Illiopolis 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 any two of the three inputs instead, the letter would range from C− to B−. The pre-1940 share is a Census survey estimate (±5.6 points). The founding year is the first post office, not a stated founding date.
Founding year: the first post office (other dates in Quick answers). 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 Illiopolis Township’s past
Read from the archive, the National Register and the record. The page puts what stands out first.
★ What stands out · Help out
Start Illiopolis Township’s collection
The first neighbors to add old photos shape how Illiopolis Township’s history is told.
Decades since 1900 with photos
00s10s20s30s40s50s60s70s80s90s
0 of 10 decades. The empty ones are waiting for someone’s album.By decade
Illiopolis Township, decade by decade
Date unknown1 to date
![Turner, Charles Alvin, 1887 (Illiopolis, Illinois) [ANS Chapman brothers business correspondence]](https://images.townratings.com/story/20489/cdcb8e21a81d1806e397-s.jpg)
Date?Today1 recent
2007On the map
Illiopolis Township on the map, 1954 to 1982
Every edition of the U.S. Geological Survey’s map of Illiopolis Township. Tap a year, or press play to watch the town change.
1954Mechanicsburg sheet · 1:62,500U.S. Geological Survey historical topographic maps (public domain), via Esri’s collection of the scans. The red ring marks the center of Illiopolis Township.
People over time
Illiopolis Township, census by census
Between 395 and 1,122 people in every census since 1870.
16 censuses, 1870–2020.
U.S. Census Bureau decennial counts, from the census table on Illiopolis Township’s Wikipedia page.
Places that used to be
Old corners, places now gone and burying grounds
Old hamlets and crossroads still carry their names on the map.
Hamlets and corners on the map
Haynes
Gone or out of use
Sangamon Ordnance Plantmilitary
4cemeteries and burying grounds inside Illiopolis Township
CalvaryMostetterRiversideWilcox
Places and cemeteries from the USGS Geographic Names Information System (2021).
Stories next door
History across the town line
Each neighbor’s History grade, on the same three inputs.
Mosquito TownshipIts storynot graded: under 1,000 residents or part of its townMount Auburn TownshipIts storynot graded: under 1,000 residents or part of its townLanesville Township1 historic placenot graded: under 1,000 residents or part of its townNiantic TownshipIts storynot graded: under 1,000 residents or part of its townLake Fork TownshipIts storynot graded: under 1,000 residents or part of its town
Questions about Illiopolis Township’s history
What year was Illiopolis Township founded?
The Illiopolis Township post office opened in 1867, the earliest record of the town by name (U.S. post office records).
How does Illiopolis Township rank for history?
Illiopolis Township is more historic than 41% of U.S. towns. 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 Illiopolis Township?
20% of Illiopolis Township’s homes were built before 1940 (Census estimate, ±5.6 points), against a typical 11% for an Illinois town; the median home was built in 1971.
Memory lane
What the archives can’t tell you, neighbors can.
Start a conversation
Sources
Where this page comes from
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 Wikimedia Commons (2), Wikipedia, U.S. Geological Survey historical maps, U.S. Census counts (via Wikipedia) and the USGS Geographic Names Information System. Archive images are copied here with their credits and licenses, shown on each photo’s page. Refreshed monthly.