Oregon County Creation Dates and Parent Counties
United States 
Oregon County Creation Dates
| Name of County | Date Formed | Parent County | Progeny County |
| Baker | 22 Sep 1862 | Wasco | Malheur 1887, Union 1864 |
| Benton | 23 Dec 1847 | Polk | Lincoln 1893, Umpqua 1851 |
| Champoeg | 05 Jul 1843 | Oregon Country | Linn 1847, renamed Marion 1849 |
| Clackamas | 05 Jul 1843 | Oregon Country | Multnomah 1854, Wasco 1854 |
| Clark | 05 Jul 1843 | Oregon Country | now in Washington State |
| Clatsop | 22 Jun 1844 | Twality | Tillamook 1853 |
| Columbia | 16 Jan 1854 | Washington | none |
| Coos | 22 Dec 1853 | Umpqua, Jackson | Curry 1855 |
| Crook | 24 Oct 1882 | Wasco | Deschutes 1916, Jefferson 1914, Wheeler 1899 |
| Curry | 18 dec 1855 | Coos | none |
| Deschutes | 13 Dec 1916 | Crook | none |
| Douglas | 07 Jan 1852 | Umpqua | Wasco 1854 |
| Gilliam | 25 Feb 1885 | Wasco | Wheeler 1899 |
| Grant | 14 Oct 1864 | Wasco, Umatilla | Harney 1889, Wheeler 1899 |
| Harney | 23 Feb1 889 | Grant | none |
| Hood River | 23 Jun 1908 | Wasco | none |
| Jackson | 12 Jan 1852 | Umpqua | Coos 1853, Josephine 1856, Lake 1874, Wasco 1854 |
| Jefferson | 12 Dec 1914 | Crook | none |
| Josephine | 22 Jan 1856 | Jackson | none |
| Klamath | 17 Oct 1882 | Lake | none |
| Lake | 24 Oct 1874 | Jackson, Wasco | Klamath 1882 |
| Lane | 28 Jan 1851 | Linn, Umpqua | Wasco 1854 |
| Lewis | 09 Dec 1845 | Oregon Country | now in Washington State |
| Lincoln | 20 Feb 1893 | Benton, Polk | none |
| Linn | 28 Dec 1847 | Champoeg | Lane 1851, Umpqua 1851, Wasco 1854 |
| Malheur | 17 Feb 1887 | Baker | none |
| Marion | 03 Sep 1849 | renamed from Champoeg | Wasco 1854 |
| Morrow | 16 Feb 1885 | Umatilla | none |
| Multnomah | 22 Dec 1854 | Washington, Clackamas | none |
| Polk | 22 Dec 1845 | Yamhill | Benton 1847, Lincoln 1893, Tillamook 1853 |
| Sherman | 25 Feb 1889 | Wasco | none |
| Tillamook | 15 Dec 1853 | Clatsop, Polk, Yamhill | none |
| Twality | 05 Jul 1843 | Oregon Country | renamed Washington 1845 |
| Umatilla | 27 Sep 1862 | Wasco | Grant 1864, Morrow 1885 |
| Umpqua | 28 Jan 1851 | Benton, Linn | Coos 1853, Douglas 1852, Jackson 1852, Lane 1851, dissolved into Douglas 1863 |
| Union | 14 Oct 1864 | Baker | Wallowa 1887, Baker 1901 |
| Wallowa | 11 Feb 1887 | Union | none |
| Wasco | 11 Jan 1854 | Clackamas, Marion, Linn, Lane, Douglas | Baker 1862, Crook 1882, Gilliam 1855, Grant 1864, Hood River 1908, Lake 1874, Sherman 1889, Umatilla 1862 |
| Washington | 22 Dec 1845 | renamed from Twality | Columbia 1854, Multnomah 1854 |
| Wheeler | 17 Feb 1899 | Crook, Gilliam, Grant | none |
| Yamhill | 05 Jul 1843 | Oregon Country | Polk 1845, Tillamook 1853 |