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][3][4]
Senators who were sworn in during the middle of the two-year congressional term (up until the last senator who was not sworn in early after winning the November 1948 election) are listed at the end of the list with no number.
U.S. Senate seniority| Rank | Senator (party-state) | Seniority date | Other factors |
|---|
| 1 | Kenneth McKellar (D-TN) | March 4, 1917 |
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| 2 | Arthur Capper (R-KS) | March 4, 1919 |
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| 3 | Walter F. George (D-GA) | November 22, 1922 |
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| 4 | Carl Hayden (D-AZ) | March 4, 1927 | Former representative (15 years) |
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| 5 | Alben W. Barkley (D-KY) | Former representative (14 years) |
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| 6 | Elmer Thomas (D-OK) | Former representative (4 years), Oklahoma 21st in population (1920) |
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| 7 | Millard Tydings (D-MD) | Former representative (4 years), Maryland 28th in population (1920) |
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| 8 | Robert F. Wagner (D-NY) |
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| 9 | Arthur H. Vandenberg (R-MI) | March 31, 1928 |
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| 10 | Tom Connally (D-TX) | March 4, 1929 |
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| 11 | Wallace White (R-ME) | March 4, 1931 | Former representative (14 years) |
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| 12 | Richard Russell, Jr. (D-GA) | January 12, 1933 |
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| 13 | John Overton[8] (D-LA) | March 4, 1933 | Former representative (2 years) |
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| 14 | Elbert D. Thomas (D-UT) |
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| 15 | Harry F. Byrd Sr. (D-VA) | Former governor |
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| 16 | Pat McCarran (D-NV) |
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| 17 | Carl Hatch (D-NM) | October 10, 1933 |
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| 18 | Joseph C. O'Mahoney (D-WY) | January 1, 1934 |
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| 19 | James Murray (D-MT) | November 7, 1934 |
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| 20 | Theodore G. Bilbo[9] (D-MS) | January 3, 1935 |
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| 21 | Dennis Chavez (D-NM) | May 11, 1935 |
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| 22 | Claude Pepper (D-FL) | November 4, 1936 |
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| 23 | Edwin C. Johnson (D-CO) | January 3, 1937 | Former governor, Colorado 33rd in population (1930) |
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| 24 | Theodore F. Green (D-RI) | Former governor, Rhode Island 37th in population (1930) |
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| 25 | Styles Bridges (R-NH) | Former governor, New Hampshire 41st in population (1930) |
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| 26 | Allen J. Ellender (D-LA) |
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| 27 | Joseph Hill (D-AL) | January 11, 1938 |
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| 28 | Tom Stewart (D-TN) | November 9, 1938 |
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| 29 | Scott W. Lucas (D-IL) | January 3, 1939 | Former representative (4 years) |
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| 30 | Charles W. Tobey (R-NH) | Former representative (2 years), former governor |
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| 31 | Clyde M. Reed (R-KS) | Former governor |
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| 32 | Robert A. Taft (R-OH) | Ohio 4th in population (1930) |
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| 33 | Sheridan Downey (D-CA) | California 6th in population |
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| 34 | Alexander Wiley (R-WI) | Wisconsin 13th in population (1930) |
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| 35 | John Chandler Gurney (R-SD) | South Dakota 36th in population (1930) |
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| 36 | Charles W. Brooks (R-IL) | November 22, 1940 |
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| 37 | Ralph Owen Brewster (R-ME) | January 3, 1941 | Former governor, Maine 35th in population (1940) |
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| 38 | William Langer (R-ND) | Former governor, North Dakota 38th in population (1940) |
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| 39 | Harley M. Kilgore (D-WV) | West Virginia 27th in population (1930) |
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| 40 | Hugh A. Butler (R-NE) | Nebraska 32nd in population (1930) |
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| 41 | Ernest McFarland (D-AZ) | Arizona 43rd in population (1930) |
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| 42 | George Aiken (R-VT) | January 10, 1941 |
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| 43 | W. Lee O'Daniel (D-TX) | August 4, 1941 |
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| 44 | Burnet R. Maybank (D-SC) | November 5, 1941 |
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| 45 | Eugene D. Millikin (R-CO) | December 20, 1941 |
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| 46 | Joseph H. Ball (R-MN) | January 3, 1943 | Previously a senator (2 years) |
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| 47 | James Eastland (D-MS) | Previously a senator (1 year) |
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| 48 | Harlan J. Bushfield[10] (R-SD) | Former governor, South Dakota 37th in population (1940) |
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| 49 | C. Douglass Buck (R-DE) | Former governor, Delaware 47th in population (1940) |
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| 50 | Homer S. Ferguson (R-MI) | Michigan 7th in population (1940) |
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| 51 | Albert W. Hawkes (R-NJ) | New Jersey 9th in population (1940) |
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| 52 | Edward H. Moore (R-OK) | Oklahoma 22nd in population (1940) |
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| 53 | W. Chapman Revercomb (R-WV) | West Virginia 24th in population (1940) |
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| 54 | John Little McClellan (D-AR) | Arkansas 25th in population (1940) |
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| 55 | Kenneth S. Wherry (R-NE) | Nebraska 32nd in population (1940) |
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| 56 | Edward V. Robertson (R-WY) | Wyoming 46th in population (1940) |
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| 57 | George A. Wilson (R-IA) | January 14, 1943 |
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| 58 | Guy Cordon (R-OR) | March 4, 1944 |
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| 59 | Howard A. Smith (R-NJ) | December 7, 1944 |
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| 60 | Warren G. Magnuson (D-WA) | December 14, 1944 |
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| 61 | Forrest C. Donnell (R-MO) | January 3, 1945 | Former governor, Missouri 10th in population (1940) |
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| 62 | Francis J. Myers (D-PA) | Former representative (6 years) |
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| 63 | J. William Fulbright (D-AR) | Former representative (2 years) |
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| 64 | Clyde R. Hoey (D-NC) | Former governor, North Carolina 11th in population (1940) |
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| 65 | Bourke B. Hickenlooper (R-IA) | Former governor, Iowa 20th in population (1940) |
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| 66 | Olin D. Johnston (D-SC) | Former governor, South Carolina 26th in population (1940) |
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| 67 | Homer E. Capehart (R-IN) | Indiana 12th in population (1940) |
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| 68 | Brien McMahon (D-CT) | Connecticut 31st in population (1940) |
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| 69 | Wayne Morse (R-OR) | Oregon 34th in population (1940) |
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| 70 | Glen H. Taylor (D-ID) | Idaho 42nd in population (1940) |
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| 71 | Leverett Saltonstall (R-MA) | January 4, 1945 | Former governor, Massachusetts 8th in population (1940) |
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| 72 | Milton Young (R-ND) | March 12, 1945 |
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| 73 | William F. Knowland (R-CA) | August 26, 1945 |
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| 74 | Spessard Holland (D-FL) | September 24, 1946 |
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| 75 | Ralph Flanders (R-VT) | November 1, 1946 |
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| 76 | A. Willis Robertson (D-VA) | November 6, 1946 | Former representative (13 years, 10 months) |
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| 77 | John Sparkman (D-AL) | Former representative (9 years, 10 months) |
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| 78 | Henry Dworshak (R-ID) | Former representative (8 years) |
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| 79 | John Sherman Cooper (R-KY) |
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| 80 | William B. Umstead (D-NC) | December 18, 1946 |
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| 81 | Harry P. Cain (R-WA) | December 26, 1946 |
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| 82 | Raymond E. Baldwin (R-CT) | December 27, 1946 |
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| 83 | Henry Cabot Lodge, Jr. (R-MA) | January 3, 1947 | Previously a senator (7 years, 1 month) |
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| 84 | William E. Jenner (R-IN) | Previously a senator (2 months) |
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| 85 | Edward Martin (R-PA) | Former governor, Pennsylvania 2nd in population (1940) |
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| 86 | John W. Bricker (R-OH) | Former governor, Ohio 4th in population (1940) |
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| 87 | Edward John Thye (R-MN) | Former governor, Minnesota 18th in population (1940) |
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| 88 | Herbert O'Conor (D-MD) | Former governor, Maryland 28th in population (1940) |
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| 89 | Irving Ives (R-NY) | New York 1st in population (1940) |
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| 90 | James P. Kem (R-MO) | Missouri 10th in population (1940) |
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| 91 | Joseph McCarthy (R-WI) | Wisconsin 13th in population (1940) |
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| 92 | J. Howard McGrath (R-RI) | Rhode Island 36th in population (1940) |
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| 93 | Zales Ecton (R-MT) | Montana 39th in population (1940) |
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| 94 | Arthur Vivian Watkins (R-UT) | Utah 40th in population (1940) |
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| 95 | John J. Williams (R-DE) | Delaware 47th in population (1940) |
|---|
| 96 | George W. Malone (R-NV) | Nevada 48th in population (1940) |
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| — | John C. Stennis (D-MS) | November 17, 1947 |
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| — | William C. Feazel (D-LA) | May 18, 1948 |
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| — | Vera C. Bushfield (R-SD) | October 6, 1948 |
|---|
| — | Karl Mundt (R-SD) | December 31, 1948 | Former representative (9 years) |
|---|
| — | J. Melville Broughton (D-NC) | Former governor |
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| — | Russell B. Long (D-LA) |
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1. ^[https://www.senate.gov/artandhistory/history/common/briefing/senators_chronological.htm A Chronological List of United States Senators 1789-Present], via www.Senate.gov
2. ^1921 U.S Census Report Contains 1920 Census results
3. ^1931 U.S Census Report Contains 1930 Census results
4. ^1941 U.S Census Report Contains 1940 Census results
5. ^Terms of service of senators that will expire in 1949.
6. ^Terms of service of senators that will expire in 1951.
7. ^Terms of service of senators that will expire in 1953.
8. ^Senator Overton died on May 14, 1948
9. ^Senator Bilbo died on August 21, 1947.
10. ^Senator Bushfield died on September 27, 1948