Founded in 1862, Umatilla County is one of 36 counties in the state of Oregon. Historically, Umatilla County was formed from Central portion of Wasco County. The city of Pendleton is the county seat. With FIPS code of 59, Umatilla County has a population of 79,988 and area of 3,215 square miles (8,327 km2).
List of all cities in Umatilla County, OR alphabetically
| City/Town | Postal Code | Area Code |
| Adams, OR | 97810 | 541 |
| Athena, OR | 97813 | 541 |
| Cayuse, OR | 97801 | 541 |
| Dale, OR | 97880 | 541 |
| Echo, OR | 97826 | 541 |
| Helix, OR | 97835 | 541 |
| Hermiston, OR | 97838 | 541 |
| McNary, OR | 97882 | 541 |
| Meacham, OR | 97859 | 541 |
| Milton Freewater, OR | 97862 | 541 |
| Pendleton, OR | 97801 | 541 |
| Pilot Rock, OR | 97868 | 541 |
| Stanfield, OR | 97875 | 541 |
| Ukiah, OR | 97880 | 541 |
| Umatilla, OR | 97882 | 541 |
| Weston, OR | 97886 | 541 |