Founding year: the first Mercer Township post office (Blevins & Helbock, CC0).
History grade
What drives Mercer Township’s History grade
On its age, its old homes and the National Register, Mercer Township is more historic than 85% of U.S. towns, #122 of 768 in Illinois. Its National Register listings hold the grade up; its age pulls it down.
A
HistoryA character grade: shown, never part of Mercer 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 Mercer Township’s 225 sits above most of its state (97% of Illinois towns have fewer) while its 88 historic buildings outnumber those of 89% of U.S. towns.
How sure. Graded on any two of the three inputs instead, the letter would range from B+ to A+. The pre-1940 share is a Census survey estimate (±6.1 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 Mercer Township’s past
Read from the archive, the National Register and the record. The page puts what stands out first.
Every edition of the U.S. Geological Survey’s map of Mercer Township. Tap a year, or press play to watch the town change.
1923Alexis 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 Mercer Township.
The story so far
Mercer Township, in brief
Wikipedia doesn’t have a history of Mercer Township yet. The photos, dates and memories neighbors add here are how it gets written.
Mercer Township is located in Mercer County, Illinois. As of the 2010 census, its population was 4,071 and it contained 1,873 housing units. Mercer Township changed its name from Centre Township on an unknown date sometime before 1921. Mercer Township contains Aledo, the county seat of Mercer County.
Its first post office opened in 1878. Between the 2010 and 2020 censuses its population fell from 4,071 to 3,964 (-3%).
Intro from Wikipedia. Population: U.S. Census Bureau.
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.
The Mercer Township post office opened in 1878, the earliest record of the town by name (U.S. post office records).
How does Mercer Township rank for history?
Mercer Township is more historic than 85% of U.S. towns, #122 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.
What is on the National Register in Mercer Township?
4 listings: 1 historic district, the Mercer County Fairgrounds, with 11 contributing buildings. 88 historic buildings in all.
How old are the homes in Mercer Township?
34% of Mercer Township’s homes were built before 1940 (Census estimate, ±6.1 points), against a typical 11% for an Illinois town; the median home was built in 1956.
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 the National Register of Historic Places (1), U.S. Geological Survey historical maps 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.
