County ZIP codes · Oregon · FIPS 41021
Gilliam County, OR ZIP Codes
Gilliam County, Oregon has 5 ZIP codes (Census 2020 ZCTA-county file; GeoNames postal codes, October 2026): 4 residential and 1 for PO boxes or a single organization. 2 of the residential ones lie mainly in Gilliam County and 2 mainly in a neighboring county; 3 cross the county line.
- ACS2020-24
- Census2020
Where are the ZIP codes of Gilliam County?
Source: U.S. Census Bureau, 2020 ZCTA cartographic boundaries; ACS 2020-2024 5-year estimates (B19013).
All 4 residential ZIP codes in Gilliam County
2 ZIP codes lie mainly in Gilliam County; 2 more reach into it from a neighboring county and follow the first table.
| In this county | ||||||
|---|---|---|---|---|---|---|
| 97823 | Condon | 1,014 | 1 | $58k | $151k | 98% |
| 97812 | Arlington | 932 | 2 | $77k | $294k | 100% |
Partly in Gilliam County
Source: U.S. Census Bureau, ACS 2020-2024 5-year estimates; county shares by land area (Census 2020 ZCTA-county relationship file).
Which ZIP codes cross the county line?
3 ZIP codes of Gilliam County extend into another county. A ZIP code follows mail routes, not county borders.
| ZIP | In Gilliam | Elsewhere |
|---|---|---|
| 97823 | 98% | Wheeler County 2% |
| 97843 | 5% | Morrow County 95% |
| 97830 | 13% | Wheeler County 87% |
Source: U.S. Census Bureau, 2020 ZCTA-county relationship file (shares of land area).
PO Box and single-organization ZIP codes
| ZIP | Postal name |
|---|---|
| 97861 | Mikkalo |
Source: GeoNames postal codes (CC BY 4.0).
Which first three digits do Gilliam County's ZIP codes use?
The first three digits of a ZIP code name the sectional center, the mail processing plant that sorts it. Every ZIP code of Gilliam County starts with 978.
| Prefix | Sectional center | Here | All codes |
|---|---|---|---|
| 978 | Portland, OR (SCF 970) | 5 | 54 |
Source: U.S. Postal Service, labeling list L005 (3-digit ZIP Code prefix groups, SCF sortation), effective October 1, 2026.