O’Brien County is a county in Iowa, United States, on the rolling farmland of the state’s northwest corner. It had a population of 14,182 at the 2020 census and covers 573 square miles (1,480 km2) of mostly land, centred near 43°04′53″N 95°37′34″W.
Primghar is the county seat, and its postal code is 51245. The county has eight incorporated cities and towns, five long-established unincorporated communities plus a handful of smaller rural place-names, and 16 civil townships. O’Brien County sits in the Central time zone.
Towns & Villages in O’Brien County
O’Brien County has eight incorporated cities, none large enough to carry a “town” designation under Iowa law, plus roughly nine unincorporated communities scattered across its townships. The table below uses City for every incorporated municipality (the seat marked City · seat) and Unincorp. for places with no municipal government.
| Place | Type | Township | Pop. | ZIP |
|---|---|---|---|---|
| Primghar | City · seat | Union | 896 | 51245 |
| Sheldon | City | Center | 5,251 | 51201 |
| Hartley | City | Hartley | 1,605 | 51346 |
| Sanborn | City | Waterman | 1,392 | 51248 |
| Paullina | City | Grant | 982 | 51046 |
| Sutherland | City | Floyd | 629 | 51058 |
| Calumet | City | Summit | 146 | 51009 |
| Archer | City | Carroll | 117 | 51231 |
| Gaza | Unincorp. | Baker | — | — |
| Germantown | Unincorp. | Dale | — | — |
| Moneta | Unincorp. | Franklin | — | — |
| Plessis | Unincorp. | Omega | — | — |
| Ritter | Unincorp. | Highland | — | — |
| Max | Unincorp. | Liberty | — | — |
| Mapleside | Unincorp. | Caledonia | — | — |
| Philby | Unincorp. | Lincoln | — | — |
| Waterman | Unincorp. | Waterman | — | — |
Sheldon straddles the O’Brien–Sioux county line; the population figure above is its combined citywide total, and the bulk of the city lies on the O’Brien County side. Waterman is both a township name and a small rural place within that township, a pairing that repeats in a few other O’Brien townships.
Townships
| Township | Pop. (2020) | Main settlements |
|---|---|---|
| Center | — | Sheldon (part) |
| Hartley | — | Hartley |
| Waterman | — | Sanborn, Waterman |
| Grant | — | Paullina |
| Union | — | Primghar |
| Floyd | — | Sutherland |
| Summit | — | Calumet |
| Carroll | — | Archer |
| Baker | — | Gaza |
| Dale | — | Germantown |
| Franklin | — | Moneta |
| Omega | — | Plessis |
| Highland | — | Ritter |
| Liberty | — | Max |
| Caledonia | — | Mapleside |
| Lincoln | — | Philby |
ZIP Codes
- 51245 — Primghar (also serves Union Township)
- 51201 — Sheldon (also serves Center Township and the O’Brien–Sioux county line area)
- 51346 — Hartley
- 51248 — Sanborn (also serves Waterman)
- 51046 — Paullina
- 51058 — Sutherland
- 51009 — Calumet
- 51231 — Archer
The unincorporated communities of Gaza, Germantown, Moneta, Plessis, Ritter, Max, Mapleside and Philby have no ZIP code of their own and are served by mail from the nearest city above.
Geography
O’Brien County lies on the gently rolling till plains of the Des Moines Lobe in Iowa’s northwest, drained mostly by the Little Sioux River and its tributaries. The land is almost entirely farmland, planted to corn and soybeans, with shallow creek valleys the only real relief. Of its 573 square miles, only about 0.2 square miles is water.
O’Brien County borders four other Iowa counties: Osceola County to the north, Clay County to the east, Cherokee County to the south, and Sioux County to the west.
Demographics
O’Brien County had 14,182 residents at the 2020 census, a density of about 25 people per square mile. Sheldon and Hartley are its two largest communities, together holding roughly half the county’s population. Like most of rural northwest Iowa, household income here tends to run below the Iowa median of $71,433, reflecting an economy still weighted toward agriculture rather than higher-wage manufacturing or services work.
Economy & Local Life
Row-crop and livestock farming anchor the county economy, supported by grain elevators, seed and agronomy dealers, and farm-equipment suppliers clustered in Primghar, Sheldon and Paullina. Sheldon, the county’s commercial hub, hosts Northwest Iowa Community College and a regional hospital, Sheldon Regional Medical Center, drawing shoppers and patients from across the county. Sanborn’s Corn Days and Paullina’s Old Settlers’ Days are among the county’s longest-running summer festivals.
History
O’Brien County was created by the Iowa General Assembly on January 15, 1851, one of 49 counties organized that year, and named for William Smith O’Brien, an Irish nationalist who led the failed Young Ireland uprising of 1848. Settlement came slowly until railroads reached the area in the 1870s and 1880s, after which towns such as Sheldon, Primghar and Hartley grew up around depot sites and became the county’s lasting population centers.
Getting There
U.S. Route 18 crosses the county east–west through Sheldon and Primghar, and Iowa Highway 60 runs north–south through Sheldon, giving the county its main road connections.
- Sioux City — 45 miles southwest
- Spencer — 20 miles east
- Spirit Lake — 30 miles northeast
- Sioux Falls, South Dakota — 50 miles northwest
The nearest commercial airport is Sioux Gateway Airport in Sioux City.
Frequently Asked Questions
Where is O’Brien County?
It is in northwest Iowa, bordered by Osceola, Clay, Cherokee and Sioux counties.
What is the population of O’Brien County?
O’Brien County had a population of 14,182 at the 2020 census.
How big is O’Brien County?
The county covers 573 square miles (1,480 km2).
What is the county seat of O’Brien County?
Primghar is the county seat.
How many towns are in O’Brien County?
Eight incorporated cities — Archer, Calumet, Hartley, Paullina, Primghar, Sanborn, Sheldon and Sutherland — plus several unincorporated communities.
What ZIP codes are in O’Brien County?
ZIP codes include 51245 (Primghar), 51201 (Sheldon), 51346 (Hartley), 51248 (Sanborn), 51046 (Paullina), 51058 (Sutherland), 51009 (Calumet) and 51231 (Archer).
What is O’Brien County’s largest city?
Sheldon, which straddles the O’Brien–Sioux county line, is the largest city serving the county.
More counties in this state: Towns and villages in Iowa.