Gilliam County is a county in Oregon, United States, in the north-central part of the state along the Columbia River. It had a population of 1,995 at the 2020 census and covers 1,223 square miles (3,170 km2) centred near 45°23′N 120°13′W.
Condon is the county seat and its postal code is 97823. The county has 3 incorporated cities (Arlington, Condon and Lonerock) plus 5 unincorporated communities, no civil townships, and observes Pacific time. Gilliam is one of Oregon’s least populous counties.
Towns & Villages in Gilliam County
Gilliam County has 8 named places on record: 3 incorporated cities and 5 unincorporated communities scattered across dryland wheat country. Type legend: City · seat, City, Unincorp.
| Place | Type | Pop. | ZIP |
|---|---|---|---|
| Condon | City · seat | — | 97823 |
| Arlington | City | — | 97812 |
| Lonerock | City | — | — |
| Mikkalo | Unincorp. | — | 97861 |
| Clem | Unincorp. | — | — |
| Mayville | Unincorp. | — | — |
| Olex | Unincorp. | — | — |
| Rock Creek | Unincorp. | — | — |
Lonerock, one of Oregon’s smallest incorporated cities, has no dedicated ZIP code and is served by Condon’s post office. “Thirtymile,” which appeared on the old settlement list here, refers to Thirtymile Creek, a Gilliam County waterway, not a populated place, and has been dropped.
ZIP Codes
- 97823 — Condon
- 97812 — Arlington
- 97861 — Mikkalo
Lonerock, Clem, Mayville, Olex and Rock Creek have no ZIP of their own and are served by Condon or Arlington mail.
Geography
Gilliam County sits on the Columbia Plateau above the Columbia River, cut by the John Day River along its eastern edge and by Thirtymile and Rock Creek to the south. Elevation ranges from around 200 feet along the Columbia breaks in the north to over 3,000 feet on the grassland benches near the Wheeler County line in the south. The landscape is almost entirely open dryland wheat and rangeland, with little forest cover and few year-round streams outside the John Day corridor.
The county is bordered by Klickitat County, Washington, across the Columbia River to the north; Morrow County to the east; Wheeler County to the south; and Wasco and Sherman counties to the southwest and west. No incorporated city in the county sits directly on another county’s border, though Arlington’s port and rail facilities along the Columbia serve shippers from both Gilliam and neighboring counties.
Demographics
The 2020 census counted 1,995 residents, making Gilliam Oregon’s third-least populous county. Condon and Arlington are its two largest communities. Gilliam County’s median household income runs below the Oregon median of $80,160, reflecting its small, wheat- and freight-dependent economy. Population density is roughly 1.7 people per square mile, among the lowest in the state.
Economy & Local Life
Dryland wheat farming and cattle ranching anchor the county’s economy, supplemented by wind-energy development on the plateau above the Columbia. Waste Management operates the Columbia Ridge Landfill near Arlington, a large regional facility that draws municipal solid waste by rail from across the Pacific Northwest and ranks among the county’s biggest employers and property-tax contributors. Arlington’s port on the Columbia River handles grain barge traffic for the region’s wheat crop. Condon hosts the Gilliam County Fairgrounds and an annual county fair each August. Grain elevators along the BNSF and Union Pacific lines through Arlington and Condon remain a fixture of the local economy, shipping the county’s wheat crop to Columbia River terminals.
History
Gilliam County was organized on February 25, 1885, carved out of Wasco and Umatilla counties as wheat farming and sheep ranching pushed settlement across the plateau. It is named for Cornelius Gilliam, a colonel who led Oregon provisional-government volunteer forces during the 1848 Cayuse War that followed the Whitman Massacre near present-day Walla Walla. Condon, platted in 1884, was chosen as the county seat the year the county was formed and remains the county’s largest town. Arlington, on the Columbia, grew as a rail and river shipping point for the surrounding wheat country, and its original townsite was relocated uphill in the 1960s when the John Day Dam pool raised the river level.
Getting There
U.S. Route 97 crosses the county’s west edge and Interstate 84 skirts the Columbia River along the northern boundary near Arlington.
- The Dalles, Oregon — 55 miles west via I-84
- Pendleton, Oregon — 65 miles east via I-84
- Fossil, Oregon — 30 miles south via Highway 19
The nearest commercial airport is Eastern Oregon Regional Airport in Pendleton.
Frequently Asked Questions
Where is Gilliam County, Oregon?
It lies in north-central Oregon along the Columbia River, between The Dalles and Pendleton.
What is the population of Gilliam County?
1,995 residents at the 2020 census.
How big is Gilliam County?
1,223 square miles (3,170 km2), of which 1,205 square miles is land.
What is the county seat of Gilliam County?
Condon is the county seat.
How many towns are in Gilliam County?
Three incorporated cities — Condon, Arlington and Lonerock — plus five unincorporated communities.
What ZIP codes are in Gilliam County?
97823 (Condon), 97812 (Arlington) and 97861 (Mikkalo).
What is Gilliam County known for?
Dryland wheat farming and the large regional landfill near Arlington that serves much of the Pacific Northwest.
More counties in this state: Towns and villages in Oregon.