| Name | Sq.Miles | Population |
|---|---|---|
| Multnomah | 435 | 672,906 |
| Hood River | 522 | 21,284 |
| Columbia | 656 | 48,065 |
| Benton | 676 | 78,640 |
| Yamhill | 715 | 92,196 |
| Washington | 723 | 499,794 |
| Polk | 741 | 70,295 |
| Sherman | 823 | 1,749 |
| Clatsop | 827 | 36,798 |
| Lincoln | 979 | 45,994 |
| Tillamook | 1,102 | 25,277 |
| Marion | 1,183 | 305,265 |
| Gilliam | 1,204 | 1,794 |
| Coos | 1,600 | 64,711 |
| Curry | 1,627 | 22,427 |
| Josephine | 1,639 | 80,761 |
| Wheeler | 1,714 | 1,455 |
| Jefferson | 1,780 | 20,100 |
| Clackamas | 1,868 | 368,470 |
| Morrow | 2,032 | 11,666 |
| Union | 2,036 | 24,540 |
| Linn | 2,292 | 108,914 |
| Wasco | 2,381 | 23,593 |
| Jackson | 2,785 | 195,322 |
| Crook | 2,979 | 22,067 |
| Deschutes | 3,018 | 141,382 |
| Baker | 3,068 | 16,287 |
| Wallowa | 3,145 | 7,014 |
| Umatilla | 3,215 | 73,878 |
| Grant | 4,528 | 7,297 |
| Lane | 4,554 | 335,180 |
| Douglas | 5,036 | 104,202 |
| Klamath | 5,944 | 66,192 |
| Lake | 8,135 | 7,313 |
| Malheur | 9,887 | 31,330 |
| Harney | 10,134 | 6,898 |
| Total | 95,996 | 3,641,056 |
The six smallest counties have almost 40% of the population on less than 4% of the land.
The three largest counties (Harney, Malheur, Lake) have 1.25% of the population on 29.33% of the land.
Source: U. S. Census Bureau; using estimates of 2005 population.