| Rank | Senator (party-state) | Seniority date | Other factors |
|---|
| 1 | Willie Person Mangum (W-NC) [6] | November 25, 1840 | |
| 2 | John Macpherson Berrien (W-GA) [7] | March 4, 1841 | Former senator |
| 3 | Jacob Welsh Miller (W-NJ) |
| 4 | James Alfred Pearce (W-MD) | March 4, 1843 | Former representative (6 years); Maryland 15th in population (1840) |
| 5 | William Upham (W-VT) | |
| 6 | David Rice Atchison (D-MO) | October 14, 1843 | |
| 7 | Jesse D. Bright (D-IN) | March 4, 1845 | Indiana 10th in population (1840) |
| 8 | John Davis (W-MA) | March 24, 1845 |
| 9 | Thomas Jefferson Rusk (D-TX) | February 21, 1846 | |
| 10 | Samuel Houston (D-TX) | February 26, 1846 | |
| 11 | George Edmund Badger (W-NC) | November 25, 1846 |
| 12 | Andrew Pickens Butler (D-SC) | December 4, 1846 |
| 13 | James M. Mason (D-VA) | January 21, 1847 |
| 14 | Robert M. T. Hunter (D-VA) | March 4, 1847 | Former representative (8 years); Virginia 4th in population (1840) |
| 15 | Joseph Rogers Underwood (W-KY) | Former representative (8 years); Kentucky 6th in population (1840) |
| 16 | Stephen A. Douglas (D-IL) | Former representative (4 years) |
| 17 | John P. Hale (D-NH) | Former representative (2 years) |
| 18 | Alpheus Felch (D-MI) | Former governor |
| 19 | James Ware Bradbury (D-ME) | Maine 13th in population (1840) |
| 20 | Henry Stuart Foote (D-MS) | Mississippi 17th in population (1840) |
| 21 | Solomon Weathersbee Downs (D-LA) | Louisiana 19th in population (1840) |
| 22 | John Hopkins Clarke (W-RI) | Rhode Island 24th in population (1840) |
| 23 | Presley Spruance (W-DE) | Delaware 26th in population (1840) |
| 25 | Jefferson Davis (D-MS) | August 10, 1847 |
| 26 | John Bell (W-TN) | November 22, 1847 |
| 27 | Solon Borland (W-AR) | March 30, 1848 |
| 28 | William K. Sebastian (W-AR) | May 12, 1848 | |
| 29 | Hannibal Hamlin (W-ME) | June 8, 1848 | Former representative (4 years); Maine 13th in population (1840) |
| 30 | Henry Dodge (D-WI) | Former delegate (4 years); Wisconsin 28th in population (1840) |
| 31 | Isaac Pigeon Walker (D-WI) | Wisconsin 28th in population (1840) |
| 32 | William Rufus de Vane King (D-AL) | July 1, 1848 |
| 33 | Augustus Caesar Dodge (D-IA) | December 7, 1848 | Former delegate (6 years) |
| 34 | George Wallace Jones (D-IA) | Former delegate (3 years) |
| 35 | Lewis Cass (D-MI) | March 4, 1849 | Former senator |
| 36 | Salmon P. Chase (FS-OH) | |
| 37 | William Dawson (W-GA) | |
| 38 | Jackson Morton (W-FL) | |
| 39 | Moses Norris, Jr. (D-NH) | |
| 40 | William H. Seward (W-NY) | |
| 41 | Truman Smith (W-CT) | |
| 42 | Pierre Soulé (D-LA) | |
| 43 | James Whitcomb (D-IN) | |
| 44 | James Cooper (W-PA) | |
| 45 | Henry Clay (W-KY) | |
| 46 | James Shields (D-IL) | October 27, 1849 | |
| 47 | Jeremiah Clemens (D-AL) | November 30, 1849 | |
| 48 | Thomas Pratt (D-MD) | January 12, 1850 |
| 49 | Franklin Elmore (D-SC) | April 11, 1850 |
| 50 | Robert Barnwell (D-SC) | June 4, 1850 |
| 51 | Thomas Ewing (W-OH) | July 20, 1850 |
| 52 | Robert Winthrop (W-MA) | July 22, 1850 | Former representative |
| 53 | William M. Gwin (D-CA) | September 9, 1850 | Former representative |
| 54 | Robert Rhett (D-SC) | December 18, 1850 | Former representative |
| 55 | Robert Rantoul, Jr. (D-MA) | February 1, 1851 |
| 56 | Solomon Foot (R-VT) | March 4, 1851 | Former representative |
| 57 | James A. Bayard, Jr. (D-DE) | |
| 58 | Stephen Mallory (D-FL) | |
| 59 | Henry S. Geyer (W-MO) | |
| 60 | Richard Brodhead (D-PA) | Former representative |
| 61 | Charles T. James (D-RI) | |
| 62 | James C. Jones (W-TN) | |
| Benjamin Wade (W-OH) | March 15, 1851 |
| Hamilton Fish (W-NY) | December 1, 1851 | Former representative, former governor and former lieutenant governor |
| John J. McRae (D-MS) | |
| Walker Brooke (W-MS) | February 18, 1852 | |
| Stephen Adams (W-MS) | March 17, 1852 | Former representative |
| William F. De Saussure (D-SC) | May 10, 1852 | |
| Isaac Toucey (D-CT) | May 12, 1852 | |
| Robert M. Charlton (D-GA) | May 31, 1852 | |
| David Meriwether (D-KY) | July 6, 1852 | |
| Archibald Dixon (W-KY) | September 1, 1852 | |
| Charles W. Cathcart (D-IN) | December 6, 1852 | Former representative |
| Benjamin Fitzpatrick (D-AL) | January 14, 1853 | Former governor |
| Samuel Shethar Phelps (W-VT) | January 17, 1853 | |
| John Pettit (D-IN) | January 18, 1853 | Former representative |
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