Rank | Senator (party-state) | Seniority date | Other factors |
1 | Thomas Hart Benton (D-MO) | August 10, 1821 | |
2 | Ambrose Hundley Sevier (D-AR) | September 18, 1836 |
3 | William Allen (D-OH) | March 4, 1837 |
4 | Samuel Shethar Phelps (W-VT) | March 4, 1839 |
5 | Daniel Sturgeon (D-PA) | January 14, 1840 |
6 | Jabez Williams Huntington (W-CT) | May 4, 1840 |
7 | Willie Person Mangum (W-NC) | November 25, 1840 |
10 | John Macpherson Berrien (W-GA) | March 4, 1841 | Former senator (4 years) |
11 | Jacob Welsh Miller (W-NJ) | New Jersey 14th in population (1830) |
12 | Arthur Pendleton Bagby (D-AL) | November 24, 1841 |
13 | John Jordan Crittenden (W-KY) | March 31, 1842 |
14 | William Lewis Dayton (W-NJ) | July 2, 1842 |
15 | James Alfred Pearce (W-MD) | March 4, 1843 | Former representative (6 years); Maryland 15th in population (1840) |
16 | Charles Gordon Atherton (D-NH) | Former representative (6 years); New Hampshire 22nd in population (1840) |
17 | Edward Allen Hannegan (D-IN) | Former representative (4 years) |
18 | Walter Terry Colquitt (D-GA) | Former representative (1 year) |
19 | Sidney Breese (D-IL) | Illinois 14th in population (1840) |
20 | William Upham (W-VT) | Vermont 21st in population (1840) |
21 | David Rice Atchison (D-MO) | October 14, 1843 |
22 | John Fairfield (W-ME) | December 4, 1843 | Maine 13th in population (1840) |
23 | Henry Johnson (W-LA) | February 12, 1844 |
24 | Dixon Hall Lewis (D-AL) | April 22, 1844 |
25 | John Milton Niles (D-CT) | May 16, 1844 |
26 | Chester Ashley (D-AR) | November 8, 1844 |
27 | Daniel Stevens Dickinson (D-NY) | November 30, 1844 |
28 | John Adams Dix (D-NY) | January 27, 1845 |
29 | Daniel Webster (W-MA) | March 4, 1845 | Former senator (13 years) |
30 | John Middleton Clayton (W-DE) | Former senator (7 years) |
31 | Thomas Corwin (W-OH) | Former representative (9 years) |
32 | Jesse Speight (D-MS) | Former representative (8 years) |
33 | Hopkins Lacy Turney (D-TN) | Former representative (6 years) |
34 | Lewis Cass (D-MI) | Former cabinet member |
35 | Jesse D. Bright (D-IN) | Indiana 10th in population (1840) |
36 | Reverdy Johnson (W-MD) | Maryland 15th in population (1840) |
37 | Albert Collins Greene (W-RI) | Rhode Island 24th in population (1840) |
38 | Simon Cameron (D-PA) | March 13, 1845 |
39 | John Davis (W-MA) | March 24, 1845 |
40 | David Levy Yulee (D-FL) | July 1, 1845 | Former delegate |
41 | John Caldwell Calhoun (D-SC) | November 26, 1845 |
42 | Thomas Jefferson Rusk (D-TX) | February 21, 1846 | |
43 | Samuel Houston (D-TX) | February 26, 1846 | Former representative |
44 | George Edmund Badger (W-NC) | November 25, 1846 |
45 | Andrew Pickens Butler (D-SC) | December 4, 1846 |
46 | James M. Mason (D-VA) | January 21, 1847 | Former representative |
47 | Robert M. T. Hunter (D-VA) | March 4, 1847 | Former representative (8 years); Virginia 4th in population (1840) |
48 | Joseph Rogers Underwood (W-KY) | Former representative (8 years); Kentucky 6th in population (1840) |
49 | Stephen A. Douglas (D-IL) | Former representative (4 years) |
50 | John P. Hale (D-NH) | Former representative (2 years) |
51 | Alpheus Felch (D-MI) | Former governor |
52 | James Ware Bradbury (D-ME) | Maine 13th in population (1840) |
53 | Henry Stuart Foote (D-MS) | Mississippi 17th in population (1840) |
54 | Solomon Weathersbee Downs (D-LA) | Louisiana 19th in population (1840) |
55 | John Hopkins Clarke (W-RI) | Rhode Island 24th in population (1840) |
56 | Presley Spruance (W-DE) | Delaware 26th in population (1840) |
| Jefferson Davis (D-MS) | August 10, 1847 |
| Roger Sherman Baldwin (W-CT)[6] | November 11, 1847 |
| John Bell (W-TN) | November 22, 1847 |
| Wyman Bradbury Seavy Moor (D-ME)[7] | January 5, 1848 |
| Herschel Vespasian Johnson (D-GA) | February 5, 1848 |
| Solon Borland (D-AR) | March 30, 1848 |
| William K. Sebastian (D-AR) | May 12, 1848 |
| Hannibal Hamlin (D-ME) | June 8, 1848 | Former representative (4 years); Maine 13th in population (1840) |
| Henry Dodge (D-WI) | Former delegate (4 years); Wisconsin 28th in population (1840) |
| Thomas Fitzgerald (D-MI) | |
| Isaac Pigeon Walker (D-WI) | Wisconsin 28th in population (1840) |
| Thomas Metcalfe (D-KY) | June 23, 1848 |
| William Rufus de Vane King (D-AL) | July 1, 1848 |
| Benjamin Fitzpatrick (D-AL) | November 25, 1848 |
| Augustus Caesar Dodge (D-IA) | December 7, 1848 | Former delegate (6 years) |
| George Wallace Jones (D-IA) | Former delegate (3 years) |
| John Wales (W-DE)[6] | February 23, 1849 |