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BHistory
History · Onarga Township

Onarga Township’s post office opened in 1854, and 43% of its homes were built before 1940

More historic than 55% of U.S. towns. What drives it

Below: 1 old photo or paper, maps from 1939 on, and the census since 1880.

1854first post office
0on the National Register
43%homes built before 1940
1old photo or paper
Add an old photoShare a memory
From Onarga Township’s archive · credits on each photo
Quick answers

How Onarga Township began

When was Onarga Township founded?

1854

The Onarga Township post office opened in 1854, the earliest record of the town by name. Another post office, Delrey (1854), opened inside today’s town and later closed.

First census: 1,061 in 18802020 census: 1,613172 years

How historic is Onarga Township?

B

More historic than 55% of U.S. towns, on its age, its old homes and the National Register.

What drives the grade ↓
Founding year: the first Onarga Township post office (Blevins & Helbock, CC0).The full story ↓
History grade

What drives Onarga Township’s History grade

On its age, its old homes and the National Register, Onarga Township is more historic than 55% of U.S. towns. Its share of homes from before 1940 holds the grade up; its National Register listings pull it down.

B
HistoryA character grade: shown, never part of Onarga Township’s overall grade.
Founding era1854, from the first post office: founded 1850–1899, an older era than 37% of U.S. townsC+Homes built before 194043.4% of homes (±7.8) · typical IL town 10.6% · U.S. 8.4%A+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 55%
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 Onarga 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 (±7.8 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 Onarga Township’s past

Read from the archive, the National Register and the record. The page puts what stands out first.

A history waiting to be writtenOnly 1 old photo is in the public archives. The rest are in attics and albums.Old housesHalf of Onarga Township’s homes were built before 1951.
★ What stands out · Help out

Start Onarga Township’s collection

The first neighbors to add old photos shape how Onarga Township’s history is told.

Decades since 1900 with photos
00s10s20s30s40s50s60s70s80s90s
0 of 10 decades. The empty ones are waiting for someone’s album.
Date a photo1 archive item has no date. Guess the decade.+2Retake an old viewAllan Pinkerton House: stand where they stood+15Share a family photoSign in to add one+10
The story

How Onarga Township came to be

From Wikipedia’s history of Onarga Township.

Read it all →

Onarga was originally laid out in the mid-19th century alongside the development of the railroad from Chicago. Because of its close proximity to Spring Creek, Onarga was one of the first settled areas of Iroquois County. The town grew rapidly but it leveled off and it now maintains small population.

The name Onarga likely comes from an Iroquois name meaning "a place of rocky hills."

Text from Wikipedia, licensed CC BY-SA 4.0.

Timeline

Onarga Township, 1854 to 1953

Woven from the archive, old maps, post office records, the National Register and the people born here.

  1. 19th century
  2. 1854Post officeThe Delrey post office opens
  3. 20th century
  4. 1939On the mapFirst mapped by the U.S. Geological Survey
  5. 1953Post officeThe Delrey post office closes
By decade

Onarga Township, decade by decade

Date unknown1 to date
Allan Pinkerton HouseDate?Allan Pinkerton House
Today5 recent
Onarga Township Cemetery2024Onarga Township CemeteryOnarga Theater2024Onarga TheaterOnaga, IL skyline2024Onaga, IL skylineOnarga Public Library2015Onarga Public LibraryTown of2010Town of
On the map

Onarga Township on the map, 1939 to 1986

Every edition of the U.S. Geological Survey’s map of Onarga Township. Tap a year, or press play to watch the town change.

Onarga Township on the 1939 USGS mapOnarga Township on the 1949 USGS mapOnarga Township on the 1986 USGS map1939Cissna Park 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 Onarga Township.

Then & now

Stand where they stood

No then-and-now pairs yet. Take a photo from the same spot as an old one and they appear here side by side.

Allan Pinkerton House
Retake this viewAllan Pinkerton House

Find the spot, match the angle, and add your photo. It becomes the first then-and-now pair on Onarga Township’s page.

Retake this view · +15
People over time

Onarga Township, census by census

02004006008001,0001,2001,4001,60018801900192019401960198020002020Peak: 1,469

Between 994 and 1,469 people in every census since 1880.

15 censuses, 1880–2020.

U.S. Census Bureau decennial counts, from the census table on Onarga Township’s Wikipedia page.

Places that used to be

Lost post offices, old corners and places now gone

Another post office, Delrey, opened and closed inside today’s town.

Hamlets and corners on the map
Delrey
Gone or out of use
Oak Grove SchoolschoolPrairie Chapel SchoolschoolRamsey SchoolschoolStrevey SchoolschoolWest Schoolschool

US Post Offices dataset (Blevins & Helbock, CC0). 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.

Douglas TownshipIts storyBCrescent TownshipIts storynot graded: under 1,000 residents or part of its townArtesia TownshipIts storynot graded: under 1,000 residents or part of its townRidgeland TownshipIts storynot graded: under 1,000 residents or part of its town

Questions about Onarga Township’s history

What year was Onarga Township founded?

The Onarga Township post office opened in 1854, the earliest record of the town by name (U.S. post office records).

How does Onarga Township rank for history?

Onarga Township is more historic than 55% 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 Onarga Township?

43% of Onarga Township’s homes were built before 1940 (Census estimate, ±7.8 points), against a typical 11% for an Illinois town; the median home was built in 1951.

Memory lane

What the archives can’t tell you, neighbors can.

Town Square →
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 (5), the Library of Congress (1), Wikipedia, U.S. Geological Survey historical maps, U.S. Census counts (via Wikipedia), the US Post Offices dataset (Blevins & Helbock) 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.