This is a classification of United States Senators by seniority during the 29th Congress, from March 4, 1845 to March 3, 1847.
Order of service is based on the commencement of the senator's first term. Behind this is former service as a senator (only giving the senator seniority within his or her new incoming class), service as Vice President, a House member, a Cabinet secretary, or a governor of a state. The final factor is the population of the senator's state.[1][2]
Senators who were sworn in in the middle of the two-year congressional term are listed at the end of the list with no number.
| Rank | Name (Party-State) | Seniority date | Other factors |
|---|---|---|---|
| 1 | Thomas Hart Benton (D-MO) | August 10, 1821 | |
| 2 | James Buchanan (D-PA)[3] | December 6, 1834 | |
| 3 | Robert John Walker (D-MS)[4] | 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)[5] | January 13, 1841 | |
| 12 | Levi Woodbury (D-NH)[6] | 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)[7] | Louisiana 19th in Population (1830) | |
| 20 | James Fowler 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)[8] | 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)[9] | 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 (D-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 Cabinent Member | |
| 48 | Jesse David 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) | Former Delegate | |
| 52 | James Diament Westcott, Jr. (D-FL) | July 1, 1845 | |
| Joseph Williams Chalmers (D-MS) | November 3, 1845 | ||
| 53 | John Caldwell Calhoun (D-SC) | November 26, 1845 | |
| Benning Wentworth Jenness (D-NH)[10] | December 1, 1845 | ||
| 54 | Isaac Samuels Pennybacker (D-VA)[11] | December 3, 1845 | |
| 55 | Samuel Houston (D-TX) | December 3, 1845 | Former Representative |
| 56 | Thomas Jefferson Rusk (D-TX) | ||
| Joseph Cilley (L-NH) | June 13, 1846 | ||
| George Edmund Badger (W-NC) | November 25, 1846 | ||
| Andrew Pickens Butler (D-SC) | December 4, 1846 | ||
| James Murray Mason (D-VA) | January 21, 1847 | Former Representative | |
| Pierre Soulé (D-LA) |
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