| Rank | Senator (party-state) | Seniority date | Other factors |
|---|
| 1 | Thomas Hart Benton (D-MO) | August 10, 1821 | |
| 2 | James Buchanan (D-PA) [6] | December 6, 1834 |
| 3 | Robert John Walker (D-MS) [7] | March 4, 1835 |
| 4 | Ambrose Hundley Sevier (D-AR) | September 18, 1836 |
| 5 | Thomas Clayton (W-DE) | January 9, 1837 |
| 6 | William Allen (D-OH) | March 4, 1837 |
| 7 | Samuel Shethar Phelps (W-VT) | March 4, 1839 |
| 8 | Daniel Sturgeon (D-PA) | January 14, 1840 |
| 9 | Jabez Williams Huntington (W-CT) | May 4, 1840 |
| 10 | Willie Person Mangum (W-NC) | November 25, 1840 |
| 11 | Isaac Chapman Bates (W-MA) [8] | January 13, 1841 |
| 12 | Levi Woodbury (D-NH) [9] | March 4, 1841 | Former senator (5 years) |
| 13 | John Macpherson Berrien (W-GA) | Former senator (4 years) |
| 14 | William Segar Archer (W-VA) | Former representative (15 years) |
| 15 | George Evans (W-ME) | Former representative (11 years) |
| 16 | William Woodbridge (W-MI) | Former delegate (1 year) |
| 17 | James Turner Morehead (W-KY) | Former governor |
| 18 | Jacob Welsh Miller (W-NJ) | New Jersey 14th in population (1830) |
| 19 | Alexander Barrow (W-LA) [10] | Louisiana 19th in population (1830) |
| 20 | James F. Simmons (W-RI) | Rhode Island 23rd in population (1830) |
| 21 | Arthur Pendleton Bagby (D-AL) | November 24, 1841 |
| 22 | John Jordan Crittenden (W-KY) | March 31, 1842 |
| 23 | William Lewis Dayton (W-NJ) | July 2, 1842 |
| 24 | George McDuffie (D-SC) [11] | December 23, 1842 |
| 25 | James Alfred Pearce (W-MD) | March 4, 1843 | Former representative (6 years); Maryland 15th in population (1840) |
| 26 | Charles Gordon Atherton (D-NH) | Former representative (6 years); New Hampshire 22nd in population (1840) |
| 27 | Edward Allen Hannegan (D-IN) | Former representative (4 years) |
| 28 | Walter Terry Colquitt (D-GA) | Former representative (1 year) |
| 29 | William Henry Haywood, Jr. (D-NC) [12] | North Carolina 7th in population (1840) |
| 30 | Sidney Breese (D-IL) | Illinois 14th in population (1840) |
| 31 | William Upham (W-VT) | Vermont 21st in population (1840) |
| 32 | David Rice Atchison (D-MO) | October 14, 1843 |
| 33 | Spencer Jarnagin (W-TN) | October 17, 1843 |
| 34 | John Fairfield (W-ME) | December 4, 1843 | Maine 13th in population (1840) |
| 35 | James Semple (D-IL) | Illinois 14th in population (1840) |
| 36 | Henry Johnson (W-LA) | February 12, 1844 |
| 37 | Dixon Hall Lewis (D-AL) | April 22, 1844 |
| 38 | John Milton Niles (D-CT) | May 16, 1844 |
| 39 | Chester Ashley (D-AR) | November 8, 1844 |
| 40 | Daniel Stevens Dickinson (D-NY) | November 30, 1844 |
| 41 | John Adams Dix (D-NY) | January 27, 1845 |
| 42 | Daniel Webster (W-MA) | March 4, 1845 | Former senator (13 years) |
| 43 | John Middleton Clayton (W-DE) | Former senator (7 years) |
| 44 | Thomas Corwin (W-OH) | Former representative (9 years) |
| 45 | Jesse Speight (D-MS) | Former representative (8 years) |
| 46 | Hopkins Lacy Turney (D-TN) | Former representative (6 years) |
| 47 | Lewis Cass (D-MI) | Former cabinet member |
| 48 | Jesse D. Bright (D-IN) | Indiana 10th in population (1840) |
| 49 | Reverdy Johnson (W-MD) | Maryland 15th in population (1840) |
| 50 | Albert Collins Greene (W-RI) | Rhode Island 24th in population (1840) |
| Simon Cameron (D-PA) | March 13, 1845 |
| John Davis (W-MA) | March 24, 1845 |
| 51 | David Levy Yulee (D-FL) | July 1, 1845 | Former delegate |
| 52 | James Diament Westcott, Jr. (D-FL) |
| Joseph Williams Chalmers (D-MS) | November 3, 1845 |
| 53 | John Caldwell Calhoun (D-SC) | November 26, 1845 |
| Benning Wentworth Jenness (D-NH) [13] | December 1, 1845 |
| 54 | Isaac Samuels Pennybacker (D-VA) [14] | December 3, 1845 |
| 55 | Thomas Jefferson Rusk (D-TX) | February 21, 1846 | |
| 56 | Samuel Houston (D-TX) | February 26, 1846 | |
| Joseph Cilley (L-NH) | June 13, 1846 |
| George Edmund Badger (W-NC) | November 25, 1846 |
| Andrew Pickens Butler (D-SC) | December 4, 1846 |
| James M. Mason (D-VA) | January 21, 1847 | Former representative |
| Pierre Soulé (D-LA) |
|
