| CONGRESS | SENATOR | TERM BEGAN | TERM ENDED | COMMENTS |
|---|---|---|---|---|
| Class 2 | ||||
| 51st-56th | George L. Shoup (R) | Dec. 18, 1890 | Mar. 3, 1901 | |
| 57th-59th | Fred T. Dubois (R) | Mar. 4, 1901 | Mar. 3, 1907 | |
| 60th-76th | William E. Borah (R) | Mar. 4, 1907 | Jan. 19, 1940 | Died |
| 76th-79th | John Thomas (R) | Jan. 27, 1940 | Nov. 10, 1945 | Appointed, then elected; died |
| 79th | Charles C. Gossett (D) | Nov. 17, 1945 | Nov. 5, 1946 | Appointed |
| 79th-80th | Henry C. Dworshak (R) | Nov. 6, 1946 | Jan. 3, 1949 | |
| 81st | Bert H. Miller (D) | Jan. 3, 1949 | Oct. 8, 1949 | Died |
| 81st-87th | Henry C. Dworshak (R) | Oct. 14, 1949 | Jul. 23, 1962 | Appointed, then elected; died |
| 87th-92nd | Leonard B. Jordan (R) | Aug. 6, 1962 | Jan. 3, 1973 | Appointed, then elected |
| 93rd-101st | James A. McClure (R) | Jan. 3, 1973 | Jan. 3, 1991 | |
| 102nd-110th | Larry E. Craig (R) | Jan. 3, 1991 | Jan. 3, 2009 | |
| 111th- | Jim Risch (R) | Jan. 3, 2009 | Present | |
| Class 3 | ||||
| 51st-52nd | William J. McConnell (R) | Dec. 18, 1890 | Mar. 3, 1891 | |
| 53rd-54th | Fred T. Dubois (R) | Mar. 4, 1891 | Mar. 3, 1897 | |
| 55th-57th | Henry Heitfeld (PO, D) | Mar. 4, 1897 | Mar. 3, 1903 | |
| 58th-62nd | Weldon B. Heyburn (R) | Mar. 4, 1903 | Oct. 17, 1912 | Died |
| 62nd | Kirtland I. Perky (D) | Nov. 18, 1912 | Feb. 5, 1913 | Appointed |
| 62nd-65th | James H. Brady (R) | Feb. 6, 1913 | Jan. 13, 1918 | Died |
| 65th-66th | John F. Nugent (D) | Jan. 22, 1918 | Jan. 14, 1921 | Appointed, then elected; resigned |
| 66th-70th | Frank R. Gooding (R) | Jan. 15, 19211 | Jun. 24, 1928 | Died |
| 70th-72nd | John Thomas (R) | Jun. 30, 1928 | Mar. 3, 1933 | Appointed, then elected |
| 73rd-75th | James P. Pope (D) | Mar. 4, 1933 | Jan. 3, 1939 | |
| 76th-78th | D. Worth Clark (D) | Jan. 3, 1939 | Jan. 3, 1945 | |
| 79th-81st | Glen H. Taylor (D) | Jan. 3, 1945 | Jan. 3, 1951 | |
| 82nd-84th | Herman Welker (R) | Jan. 3, 1951 | Jan. 3, 1957 | |
| 85th-96th | Frank F. Church (D) | Jan. 3, 1957 | Jan. 3, 1981 | |
| 97th-102nd | Steven D. Symms (R) | Jan. 3, 1981 | Jan. 3, 1993 | |
| 103rd-105th | Dirk Kempthorne (R) | Jan. 3, 1993 | Jan. 3, 1999 | |
| 106th- | Mike Crapo (R) | Jan. 3, 1999 | Present | |
1. Appointed to fill the remainder of the term expiring Mar. 3, 1921 having been elected to the term beginning Mar. 3, 1921.
