The names of current senators appear in bold print.
| Name/State | Party | Years | |
|---|---|---|---|
 | Hayne, Robert Y. (SC) | Nullifier | 1831-1832 |
 | Miller, Stephen D. (SC) | Nullifier | 1831-1833 |
 | Calhoun, John C. (SC) | Nullifier | 1832-1837 |
 | Preston, William C. (SC) | Nullifier | 1833-1837 |
 | Francis, John B. (RI) | Law and Order | 1844-1845 |
 | Cilley, Joseph (NH) | Liberty | 1846-1847 |
 | Hale, John P. (NH) | Independent Democrat | 1847-1849 |
| Hale, John P. (NH) | Free Soil | 1849-1853 |
 | Chase, Salmon P. (OH) | Free Soil | 1849-1855 |
 | Sumner, Charles (MA) | Free Soil | 1851-1855 |
 | Brainerd, Lawrence (VT) | Free Soil | 1854-1855 |
 | Gillette, Francis (CT) | Free Soil | 1854-1855 |
 | Wilson, Henry (MA) | American | 1855 |
 | Houston, Sam (TX) | American | 1855-1859 |
 | Bell, John (TN) | American | 1857-1859 |
 | Thompson, John B. (KY) | American | 1857-1859 |
 | Crittenden, John J. (KY) | American | 1857-1861 |
 | Kennedy, Anthony (MD) | American | 1857-1861 |
| Kennedy, Anthony (MD) | Unionist | 1861-1863 |
 | Willey, Waitman T. (VA) | Unionist | 1861-1863 |
 | Carlile, John S. (VA) | Unionist | 1861-1865 |
 | Davis, Garrett (KY) | Unionist | 1861-1865 |
 | Henderson, John B. (MO) | Unionist | 1862-1863 |
 | Hicks, Thomas H. (MD) | Unionist | 1862-1863 |
 | Wilson, Robert (MO) | Unionist | 1862-1863 |
 | Wright, Joseph A. (IN) | Unionist | 1862-1863 |
 | Bowden, Lemuel J. (VA) | Unionist | 1863-1864 |
 | Brown, Benjamin Gratz (MO) | Unconditional Unionist | 1863-1865 |
| Henderson, John B. (MO) | Unconditional Unionist | 1863-1865 |
| Hicks, Thomas H. (MD) | Unconditional Unionist | 1863-1865 |
 | Johnson, Reverdy (MD) | Unionist | 1863-1865 |
| Willey, Waitman T. (WV) | Unconditional Unionist | 1863-1865 |
 | Van Winkle, Peter G. (WV) | Unconditional Unionist | 1863-1867 |
 | Creswell, John A.J. (MD) | Unconditional Unionist | 1865-1867 |
 | Fowler, Joseph S. (TN) | Unconditional Unionist | 1865-1867 |
 | Patterson, David T. (TN) | Unionist | 1865-1867 |
 | Schurz, Carl (MO) | Liberal Republican | 1871-1875 |
| Sumner, Charles (MA) | Liberal Republican | 1873-1874 |
 | Fenton, Reuben E. (NY) | Liberal Republican | 1873-1875 |
 | Ferry, Orris S. (CT) | Liberal Republican | 1873-1875 |
 | Hamilton, Morgan C. (TX) | Liberal Republican | 1873-1875 |
 | Sprague, William (RI) | Liberal Republican | 1873-1875 |
 | Tipton, Thomas W. (NE) | Liberal Republican | 1873-1875 |
 | Booth, Newton (CA) | Independent Republican | 1875-1877 |
 | Davis, David (IL) | Independent | 1877-1883 |
 | Mahone, William (VA) | Readjuster | 1881-1885 |
 | Riddleberger, Harrison H. (VA) | Readjuster | 1883-1885 |
 | Peffer, William A. (KS) | Populist | 1891-1897 |
 | Kyle, James H. (SD) | Populist | 1891-1901 |
 | Allen, William V. (NE) | Populist | 1893-1901 |
 | Stewart, William M. (NV) | Silver | 1893-1901 |
 | Butler, Marion (NC) | Populist | 1895-1901 |
 | Jones, John P. (NV) | Silver | 1895-1901 |
 | Cannon, Frank J. (UT) | Silver Republican | 1896-1899 |
 | Mantle, Lee (MT) | Silver Republican | 1896-1899 |
 | Pettigrew, Richard F. (SD) | Silver Republican | 1896-1901 |
 | Teller, Henry M. (CO) | Silver Republican | 1896-1901 |
 | Heitfeld, Henry (ID) | Populist | 1897-1901 |
 | Turner, George (WA) | Silver Republican | 1897-1901 |
 | Harris, William A. (KS) | Populist | 1897-1903 |
 | Poindexter, Miles (WA) | Progressive | 1913-1915 |
 | Johnson, Magnus (MN) | Farmer-Labor | 1923-1925 |
 | Shipstead, Henrik (MN) | Farmer-Labor | 1923-1941 |
 | Benson, Elmer A. (MN) | Farmer-Labor | 1935-1936 |
 | La Follette, Robert M., Jr. (WI) | Progressive | 1935-1947 |
 | Lundeen, Ernest (MN) | Farmer-Labor | 1937-1940 |
 | Norris, George W. (NE) | Independent | 1937-1943 |
 | Morse, Wayne L. (OR) | Independent | 1953-1955 |
 | Thurmond, J. Strom (SC) | Independent Democrat | 1954-1956 |
 | Buckley, James L. (NY) | Conservative | 1971-1977 |
 | Byrd, Harry F., Jr. (VA) | Independent | 1971-1983 |
 | Smith, Bob (NH) | Independent | 19991 |
 | Jeffords, James (VT) | Independent | 2001-20072 |
 | Barkley, Dean (MN) | Independent | 2002-2003 |
 | Lieberman, Joseph I. (CT) | Independent Democrat | 1989-20133 |
 | Sanders, Bernard (VT) | Independent | 2007- |
 | King, Angus S., Jr. (ME) | Independent | 2013- |
Total: 77 individuals (Three senators, John P. Hale, Anthony Kennedy, and Waitman T. Willey, each represented two third parties at different times.)
1 Smith announced his change from the Republican party on July 13, 1999. On November 1, 1999, he announced that he was changing back to Republican. He noted that, since his home town in New Hampshire had not yet changed his voter registration, he had technically never left the Republican party.
2 Jeffords announced his change on May 24, 2001, effective June 6, 2001, indicating that he would caucus with the Democratic party, thus changing control of the evenly divided Senate from the Republicans to the Democrats.
3 Lieberman was elected as a Democrat to the U.S. Senate in 1988, and reelected in 1994 and 2000. In 2006, he lost the Democratic primary and chose to run as an Independent Democrat, winning the 2006 election under that party affiliation.
