Guest, Sign inJoin

Post to Oacoma

We’ll email a one-tap link to publish your post. No password, and nothing is public until you click it.
Already a member? Sign in
–Not graded
History · Oacoma

Oacoma’s post office opened in 1890

Most of Oacoma was built recently: 9% of its homes predate 1940 and the median home dates from 1988. Below: maps from 1935 on and the census since 1910.

1890first post office
0on the National Register
9%homes built before 1940
Add an old photoShare a memory
Photo: Runner1928 · CC BY-SA 4.0
Quick answers

How Oacoma began

When was Oacoma founded?

1890

The Oacoma post office opened in 1890, the earliest record of the town by name. Another post office, Cedarfork (1906), opened inside today’s town and later closed.

First census: 235 in 19102020 census: 386136 years
Founding year: the first Oacoma post office (Blevins & Helbock, CC0).The full story ↓

What stands out about Oacoma’s past

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

A history waiting to be writtenNo old photos of Oacoma are in the public archives yet. The rest are in attics and albums.
★ What stands out · Help out

Start Oacoma’s collection

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

Decades since 1900 with photos
00s10s20s30s40s50s60s70s80s90s
0 of 10 decades. The empty ones are waiting for someone’s album.
Share a family photoSign in to add one+10
The story

How Oacoma came to be

From Wikipedia’s history of Oacoma.

Read it all →

On September 17, 1804, Lewis and Clark camped on the west bank of the Missouri River near American Island where Oacoma is now located. During the remainder of the 19th century the area was a stopping off place for explorers, fur traders and steamboat men. The township of Oacoma was laid out in 1891 as the county seat for the newly formed Lyman County; the County seat was transferred to the town of Kennebec in 1922. The Chicago, Milwaukee, St. Paul and Pacific Railroad arrived in Oacoma in 1905, and Oacoma was known as a "banking post-village". In the 21st century, it is a rest stop for travelers on Interstate 90.

Text from Wikipedia, licensed CC BY-SA 4.0.

Timeline

Oacoma, 1890 to 1935

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

  1. 19th century
  2. 1890Post officeThe Oacoma post office opens
  3. 20th century
  4. 1906Post officeThe Cedarfork post office opens
  5. 1913Post officeThe Cedarfork post office closes
  6. 1935On the mapFirst mapped by the U.S. Geological Survey
By decade

Oacoma, decade by decade

Today6 recent
I-90 Business Loop bridge across Missouri River2014I-90 Business Loop bridge across Missouri RiverBecket Mass Sign2014Becket Mass SignErosion control blocks of Sioux Quartzite (Paleoproterozoic, 1.65-1.70 Ga; Interstate 90 at the Missouri River2012Erosion control blocks of Sioux Quartzite (Paleoprote…Al's Oasis2009Al's OasisMotorcycle rider next to Missouri River between Chamberlain and2007Motorcycle rider next to Missouri River between Chamb…SDMap-doton-Oacoma2004SDMap-doton-Oacoma
On the map

Oacoma on the map, 1935 to 1952

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

Oacoma on the 1935 USGS mapOacoma on the 1952 USGS map1935Chamberlain 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 Oacoma.

People over time

Oacoma, census by census

0100200300400500192019401960198020002020Peak: 451

Between 167 and 451 people in every census since 1910.

12 censuses, 1910–2020.

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

Famous people

Famous people close to Oacoma

Nobody well known was born in Oacoma itself, so here are the best known from just nearby.

See all →
E
Eddie SpearsAmerican actor · b. 1982
Julia Anna GardnerAmerican geologist · b. 1882
E
Elizabeth Cook-LynnSioux writer and editor · b. 1930
Travis LutterAmerican mixed martial artist · b. 1973
E
Elizabeth ColborneAmerican printmaker, illustrator · b. 1885
B
Barry FrenchAmerican football player · b. 1922
Places that used to be

Lost post offices, places now gone and burying grounds

Oacoma’s post office has been open since 1890. Another post office, Cedarfork, opened and closed inside today’s town.

Oacoma
1890–today
Cedarfork
1906–1913
18901960today
Gone or out of use
Fort Recoverylocale
1cemetery inside Oacoma
Oacoma

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.

Oacoma TownshipIts storynot graded: under 1,000 residents or part of its townChamberlain Township1 historic placenot graded: under 1,000 residents or part of its townChamberlain2 historic placesB−

Questions about Oacoma’s history

What year was Oacoma founded?

The Oacoma post office opened in 1890, the earliest record of the town by name (U.S. post office records).

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). How TownRatings grades history →

From Wikimedia Commons (6), 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.