| Shoup, George L. (Republican) | 1890 to December 1890 | 
| Willey, N.B. (Republican) | December 1890 to January 1893 | 
| McConnell, William J. (Republican) | January 1893 to January 4, 1897 | 
| Steunenberg, Frank (P-D) | January 4, 1897 to January 7, 1901 | 
| Hunt, Frank W. (Democrat) | January 7, 1901 to January 5, 1903 | 
| Morrison, John T. (Republican) | January 5, 1903 to January 2, 1905 | 
| Gooding, Frank R. (Republican) | January 3, 1905 to January 4, 1909 | 
| Brady, James H. (Republican) | January 4, 1909 to January 2, 1911 | 
| Hawley, James H. (Democrat) | January 2, 1911 to January 6, 1913 | 
| Haines, John M. (Republican) | January 6, 1913 to January 4, 1915 | 
| Alexander, Moses (Democrat) | January 4, 1915 to January 6, 1919 | 
| Davis, D.W. (Republican) | January 6, 1919 to January 1, 1923 | 
| Moore, Charles C. (Republican) | January 3, 1923 to January 3, 1927 | 
| Baldridge, H.C. (Republican) | January 3, 1927 to January 5, 1931 | 
| Ross, C. Ben (Democrat) | January 5, 1931 to January 4, 1937 | 
| Clark, Barzilla W. (Democrat) | January 4, 1937 to January 2, 1939 | 
| Bottolfsen, C.A. (Republican) | January 1, 1939 to January 5, 1941 | 
| Clark, Chase A. (Democrat) | January 6, 1941 to January 4, 1943 | 
| Bottolfsen, C.A. (Republican) | January 4, 1943 to January 1, 1945 | 
| Gossett, Chas. C. (Democrat) | January 1, 1945 to November 17, 1945 | 
| Williams, Arnold (Democrat) | November, 17 1945 to January 6, 1947 | 
| Robins, Dr. C.A. (Republican) | January 6, 1947 to January 1, 1951 | 
| Jordan, Len B. (Republican) | January 1, 1951 to January 3, 1955 | 
| Smylie, Robert E. (Republican) | January 3,1955 to January 2, 1967 | 
| Samuelson, Don (Republican) | January 2, 1967 to January 4, 1971 | 
| Andrus, Cecil D. (Democrat) | January 4, 1971 to January 24, 1977 | 
| Evans, John V. (Democrat) | January 24, 1977 to January 5, 1987 | 
| Andrus, Cecil D. (Democrat) | January 5, 1987 to January 1, 1995 | 
| Batt, Phillip E. (Republican) | January 2, 1995 to January 3, 1999 | 
| Kempthorne, Dirk (Republican) | January 4, 1999 to May 25, 2006 | 
| Risch, James E. (Republican) | May 26, 2006 to January 1, 2007 | 
| Otter, C.L. “Butch” (Republican) | January 1, 2007 to January 7, 2019 | 
| Little, Brad (Republican) | January 7, 2019 to present |