| CONGRESS | SENATOR | TERM BEGAN | TERM ENDED | COMMENTS |
|---|---|---|---|---|
| Class 1 | ||||
| 30th-34th | Henry Dodge (D) | Jun. 8, 1848 | Mar. 3, 1857 | |
| 35th-40th | James R. Doolittle (R) | Mar. 4, 1857 | Mar. 3, 1869 | |
| 41st-43rd | Matthew H. Carpenter (R) | Mar. 4, 1869 | Mar. 3, 1875 | |
| 44th-46th | Angus Cameron (R) | Mar. 4, 1875 | Mar. 3, 1881 | |
| 47th-52nd | Philetus Sawyer (R) | Mar. 4, 1881 | Mar. 3, 1893 | |
| 53rd-55th | John L. Mitchell (D) | Mar. 4, 1893 | Mar. 3, 1899 | |
| 56th-58th | Joseph V. Quarles (R) | Mar. 4, 1899 | Mar. 3, 1905 | |
| 59th-69th | Robert M. La Follette (R) | Jan. 4, 19061 | Jun. 18, 1925 | Died |
| 69th-79th | Robert M. La Follette Jr. (R, PR) | Sept. 30, 1925 | Jan. 3, 1947 | |
| 80th-85th | Joseph R. McCarthy (R) | Jan. 3, 1947 | May 2, 1957 | Died |
| 85th-100th | William Proxmire (D) | Aug. 28, 1957 | Jan. 3, 1989 | |
| 101st-112th | Herbert H. Kohl (D) | Jan. 3, 1989 | Jan. 3, 2013 | |
| 113th- | Tammy Baldwin (D) | Jan. 3, 2013 | Present | |
| Class 3 | ||||
| 30th-33rd | Isaac P. Walker (D) | Jun. 8, 1848 | Mar. 3, 1855 | |
| 34th-36th | Charles Durkee (OP, R) | Mar. 4, 1855 | Mar. 3, 1861 | |
| 37th-45th | Timothy O. Howe (R) | Mar. 4, 1861 | Mar. 3, 1879 | |
| 46th | Matthew H. Carpenter (R) | Mar. 4, 1879 | Feb. 24, 1881 | Died |
| 47th-48th | Angus Cameron (R) | Mar. 14, 1881 | Mar. 3, 1885 | |
| 49th-51st | John Coit Spooner (R) | Mar. 4, 1885 | Mar. 3, 1891 | |
| 52nd-54th | William F. Villas (D) | Mar. 4, 1891 | Mar. 3, 1897 | |
| 55th-59th | John Coit Spooner (R) | Mar. 4, 1897 | Apr. 30, 1907 | Resigned |
| 59th-63rd | Isaac Stephenson (R) | May 17, 1907 | Mar. 3, 1915 | |
| 64th-65th | Paul O. Husting (D) | Mar. 4, 1915 | Oct. 21, 1917 | Died |
| 65th-69th | Irvine L. Lenroot (R) | Apr. 18, 1918 | Mar. 3, 1927 | |
| 70th-72nd | John J. Blaine (R) | Mar. 4, 1927 | Mar. 3, 1933 | |
| 73rd-75th | F. Ryan Duffy (D) | Mar. 4, 1933 | Jan. 3, 1939 | |
| 76th-87th | Alexander Wiley (R) | Jan. 3, 1939 | Jan. 3, 1963 | |
| 88th-96th | Gaylord A. Nelson (D) | Jan. 8, 19632 | Jan. 3, 1981 | |
| 97th-102nd | Robert W. Kasten Jr. (R) | Jan. 3, 1981 | Jan. 3, 1993 | |
| 103rd-111th | Russ D. Feingold (D) | Jan. 3, 1993 | Jan. 3, 2011 | |
| 112th- | Ron Johnson (R) | Jan. 3, 2011 | Present | |
1. Elected to term beginning Mar. 4, 1905. Continued to serve as governor before taking senate seat.
2. Elected to term beginning Jan. 3, 1963. Continued to serve as governor before taking senate seat.
