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| Year | Census date | States | U.S.A. Pop. | U.S. Census Director | Oregon Pop. | Wash. Pop. | Idaho Pop. | New States |
|---|---|---|---|---|---|---|---|---|
| 2010 | Apr 01 | 50 | 308,745,538 | Robert Martin Groves | 3,831,074 | 6,724,540 | 1,567,582 | |
| 2000 | Apr 01 | 50 | 281,421,906 | Kenneth Prewitt | 3,421,399 | 5,894,121 | 1,293,953 | |
| 1990 | Apr 01 | 50 | 248,709,873 | Barbara Everitt Bryant | 2,842,321 | 4,866,692 | 1,006,749 | |
| 1980 | Apr 01 | 50 | 226,542,199 | Vincent Barabba | 2,633,156 | 4,132,353 | 944,127 | |
| 1971 | Jul 01 | 26th Amendment lowers voting age to 18. | ||||||
| 1970 | Dec 21 | Oregon v. Mitchell decided by Supreme Court. | ||||||
| 1970 | Apr 01 | 50 | 203,302,031 | George Hay Brown | 2,091,533 | 3,413,244 | 713,015 | |
| 1960 | Apr 01 | 50 | 179,323,175 | Robert Wilbur Burgess | 1,768,687 | 2,853,214 | 667,191 | AK, HI |
| 1959 | Feb 24 | 15th Amendment belatedly ratified by Oregon. | ||||||
| 1950 | Apr 01 | 48 | 151,325,798 | Roy Victor Peel | 1,521,341 | 2,378,963 | 588,637 | |
| 1940 | Apr 01 | 48 | 132,164,569 | William Lane Austin | 1,089,684 | 1,736,191 | 524,873 | |
| 1930 | Apr 01 | 48 | 123,202,624 | William Mott Steuart | 953,786 | 1,563,396 | 445,032 | |
| 1929 | Jun 18 | Reapportionment Act limits House to 435 seats. | ||||||
| 1920 | Jan 01 | 48 | 106,021,537 | Samuel Lyle Rogers | 783,389 | 1,356,621 | 431,866 | NM, AZ |
| 1910 | Apr 15 | 46 | 92,228,496 | Edward Dana Durand | 672,765 | 1,141,990 | 325,594 | OK |
| 1900 | Jun 01 | 45 | 76,212,168 | William Rush Merriam | 413,536 | 518,103 | 161,772 | ID, WY, UT |
| 1890 | Jul 03 | Idaho became 43rd state. | ||||||
| 1890 | Jun 01 | 42 | 62,979,766 | Robert Percival Porter | 317,704 | 357,232 | 88,548 | ND, SD, MT, WA |
| 1889 | Nov 11 | Washington became 42nd state. | ||||||
| 1880 | Jun 01 | 38 | 50,189,209 | Francis Amasa Walker | 174,768 | 75,116 | 32,610 | CO |
| 1870 | Jun 01 | 37 | 38,558,371 | Francis Amasa Walker | 90,923 | 23,955 | 14,999 | KS, WV, NV, NE |
| 1863 | Mar 04 | Territory of Idaho formed. | ||||||
| 1860 | Jun 01 | 33 | 31,443,321 | Joseph C. G. Kennedy | 52,465 | 11,594 | CA, MN, OR | |
| 1859 | Feb 14 | Oregon became 33rd state. | ||||||
| 1853 | Mar 02 | Washington Territory formed. | ||||||
| 1850 | Jun 01 | 30 | 23,191,876 | Joseph C. G. Kennedy | 12,093 | Territorial counts | FL, TX, IA, WI | |
| 1848 | Aug 14 | Oregon Territory formed. | 
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| 1847 | Nov 29 | Whitman massacre. | ||||||
| 1846 | Jun 15 | Oregon Treaty signed in Washington, D.C. | ||||||
| 1843 | May 2 | Provisional Government of Oregon formed. | ||||||
| 1840 | Jun 01 | 26 | 17,063,353 | William Augustus Weaver | AR, MI | |||
| 1830 | Jun 01 | 24 | 12,860,702 | Martin Van Buren | MO | |||
| 1820 | Aug 07 | 23 | 9,638,453 | John Quincy Adams | LA, IN, MS, IL, AL, ME | |||
| 1810 | Aug 06 | 17 | 7,239,881 | Robert Smith | OH | |||
| 1800 | Aug 04 | 16 | 5,308,483 | John Marshall | VT, KY, TN | |||
| 1790 | Aug 02 | 13 | 3,929,214 | Thomas Jefferson | DE, PA, NJ, GA, CT, MA, MD, SC, NH, VA, NY, NC, RI | |||
