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BHistory
History · Eldorado

Eldorado’s post office opened in 1858, and 21% of its homes were built before 1940

More historic than 61% of U.S. towns · #321 of 768 in Illinois. What drives it

Its Register listing is the Eldorado City Hall. Below: 7 old photos and papers, maps from 1894 on, and the census since 1900.

1858first post office
1on the National Register
21%homes built before 1940
7old photos & papers
6famous people
Add an old photoShare a memory
From Eldorado’s archive · credits on each photo
Quick answers

How Eldorado began

When was Eldorado founded?

1858

The Eldorado post office opened in 1858, the earliest record of the town by name.

First census: 1,445 in 19002020 census: 3,743168 years

How historic is Eldorado?

B

More historic than 61% of U.S. towns, on its age, its old homes and the National Register.

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

What drives Eldorado’s History grade

On its age, its old homes and the National Register, Eldorado is more historic than 61% of U.S. towns, #321 of 768 in Illinois. Its share of homes from before 1940 holds the grade up; its age pulls it down.

B
HistoryA character grade: shown, never part of Eldorado’s overall grade.
Founding era1858, from the first post office: founded 1850–1899, an older era than 37% of U.S. townsC+Homes built before 194021.4% of homes (±4.8) · typical IL town 10.6% · U.S. 8.4%B+National Register1 listing, 2.7 per 10,000 residents · typical IL town 0.5 · U.S. 2.4B
All U.S. towns we grade (21,289)Ahead of 61%
NewerOlder
Illinois towns of 2,500+ (768)Ahead of 58%

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 Eldorado’s 2.7 sits above most of its state (69% of Illinois towns have fewer) while its 1 listings outnumber those of 51% 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 (±4.8 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 Eldorado’s past

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

Boom and bustPeaked at 5,198 in 1980; 3,743 people lived here in 2020.Mapped building by building5 fire insurance maps, 1894 to 1919, drew every building in Eldorado.Old housesHalf of Eldorado’s homes were built before 1961.
★ What stands out · People over time

Eldorado, census by census

05001,0001,5002,0002,5003,0003,5004,0004,5005,0005,5001900192019401960198020002020Peak: 5,198

Peaked at 5,198 in 1980; 3,743 people lived here in 2020.

13 censuses, 1900–2020.

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

Every building

Eldorado, building by building, 1894–1919

Fire insurance maps drew every building, what it was made of and what it was used for, so insurers could price the risk of fire. Pick a year, then a sheet.

Eldorado fire insurance map, 1894, sheet 21894Sheet 2 of 2
Edition
BrickWoodStone

Sanborn Map Company, via the Library of Congress. Editions published in 1930 or earlier, which are in the public domain.

The story

How Eldorado came to be

From Wikipedia’s history of Eldorado.

Read it all →

Eldorado was first platted on May 24, 1858, by a surveyor named Martin D. Gillett. The post office was established on December 8 of that same year. Just before the Civil War, the first businesses were started in the town. The original village was incorporated in 1870. It was founded by Francis Elder and his neighbors who were brothers William and John Reed.

ChaptersRace relations

Text from Wikipedia, licensed CC BY-SA 4.0.

Timeline

Eldorado, 1858 to 1980

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

  1. 19th century
  2. 1858Post officeThe Eldorado post office opens
  3. 20th century
  4. 1905On the mapFirst mapped by the U.S. Geological Survey
  5. 1937In the archiveCupboard
  6. 1943Born hereKendall Rhine is born here
  7. 1947Born hereDavid D. Phelps is born here
  8. 1951Born hereGeorge Barker is born here
  9. 1954Born hereJeanette Mott Oxford is born here
  10. 1980CensusPopulation peaks at 5,198
By decade

Eldorado, decade by decade

One decade in the archive so far: the 1930s. Scroll each row; tap a photo for its story.

1930s7 items
Cupboard1937CupboardGoing to town. Near Eldorado, Illinois1937Going to town. Near Eldorado, IllinoisOld square piano in a home at Eldorado, Illinois1937Old square piano in a home at Eldorado, IllinoisEarly American secretary in a home at Eldorado, Illinois1937Early American secretary in a home at Eldorado, Illin…Shopping center of Eldorado, Illinois1939Shopping center of Eldorado, IllinoisMoving picture theaters charge only five cents for admission, indicating a poor population1939Moving picture theaters charge only five cents for ad…Rehabilitation Administration supervisor with client. Ridgeway, Illinois1939Rehabilitation Administration supervisor with client.…
1940s–1990snothing yet
Nothing in the archives for these yearsWeddings on Main Street, storms, parades, school pictures, the old store. If it’s in your family album, it belongs here.
Add from your album
Today3 recent
Eldorado City Hall2017Eldorado City Hall2010 Census Urban Cluster Reference Map for20102010 Census Urban Cluster Reference Map forBookEldorado IL Museum2007Eldorado IL Museum
On the map

Eldorado on the map, 1905 to 1963

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

Eldorado on the 1905 USGS mapEldorado on the 1963 USGS map1905Eldorado 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 Eldorado.

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.

Cupboard
Retake this viewCupboard, 1937

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

Retake this view · +15
On the National Register

1 historic place in Eldorado

The country’s official list of buildings and places worth saving.

place listed
1
National Historic Landmarks
0
none yet
historic buildings protected
1
each building in a district counts
first listed
1995
Eldorado City Hall
Eldorado City Hall
Buildings

Architectural styles listings

Classical Revival1
Eldorado City HallClassical Revival

National Park Service, National Register of Historic Places. Photos from Wikimedia Commons, credited on each place’s page.

Famous people

6 famous people were born in Eldorado

Writers, athletes, leaders and more, ranked by how widely they’re known.

See all →
David D. PhelpsAmerican politician · b. 1947
Kendall RhineAmerican basketball player · b. 1943
George BarkerAmerican politician in Virginia · b. 1951
J
Jeanette Mott OxfordAmerican politician · b. 1954
Brandon W. PhelpsAmerican politician · b. 1970
L
Lynda Lee KaidAmerican professor · b. 1948
Places that used to be

Old corners and places now gone

Eldorado’s post office has been open since 1858.

Hamlets and corners on the map
Beulah HeightsSaline City
Gone or out of use
Beulah Heights Methodist ChurchchurchBeulah Heights Public SchoolschoolLincoln Public Schoolschool

US Post Offices dataset (Blevins & Helbock, CC0). Places and cemeteries from the USGS Geographic Names Information System (2021).

Help out

Finish Eldorado’s story

Most archives stop around 1920. The photos from after that are in family albums, not libraries.

Decades since 1900 with photos
00s10s20s30s40s50s60s70s80s90s
1 of 10 decades. The empty ones are waiting for someone’s album.
Retake an old viewCupboard: stand where they stood+15Share a family photoSign in to add one+10

Questions about Eldorado’s history

What year was Eldorado founded?

The Eldorado post office opened in 1858, the earliest record of the town by name (U.S. post office records).

How does Eldorado rank for history?

Eldorado is more historic than 61% of U.S. towns, #321 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 Eldorado?

One place: the Eldorado City Hall (listed 1995).

How old are the homes in Eldorado?

21% of Eldorado’s homes were built before 1940 (Census estimate, ±4.8 points), against a typical 11% for an Illinois town; the median home was built in 1961.

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 (3), the Library of Congress (7), Wikidata (1), the National Register of Historic Places (1), Wikipedia, Wikidata and Wikipedia for famous people, U.S. Geological Survey historical maps, U.S. Census counts (via Wikipedia), the US Post Offices dataset (Blevins & Helbock), the USGS Geographic Names Information System and Sanborn fire insurance maps (Library of Congress). Archive images are copied here with their credits and licenses, shown on each photo’s page. Refreshed monthly.