Senator

Dates of Service

Length of Service

1. Robert C. Byrd (D-WV)

January 3, 1959 to present

49 years, 8 months

2. Strom Thurmond (R-SC)

December 24, 1954 to April 4, 1956

and November 7, 1956 to January 3, 2003

47 years, 5.2 months

3. Edward M. Kennedy (D-MA)

November 7, 1962 to present

45 years, 10 months

4. Daniel K. Inouye (D-HI)

January 3, 1963-present

45 years, 8 months

5. Carl T. Hayden (D-AZ)

March 4, 1927 to January 3, 1969

41 years, 10.1 months

6. John C. Stennis (D-MS)

November 5, 1947 to January 3, 1989

41 years, 2 months

7. Theodore F. Stevens (R-AK)

December 24, 1968 to present

39 years, 8 months

8. Ernest F. Hollings (D-SC)

November 9, 1966 to January 3, 2005

38 years, 1.8 months

9. Richard B. Russell (D-GA)

January 12, 1933 to January 21, 1971

38 years

10. Russell B. Long (D-LA)

December 31, 1948 to January 3, 1987

38 years

11. Francis E. Warren (R-WY)

November 18, 1890 to March 3, 1893

and March 4, 1895 to November 24, 1929

37 years

12. James O. Eastland (D-MS)

June 30, 1941 to September 28, 1941

and January 3, 1943 to December 27, 1978

36 years, 3 months

13. Warren Magnuson (D-WA)

December 14, 1944 to January 2, 1981

36 years

14. Claiborne Pell (D-RI)

January 3, 1961 to January 3, 1997

36 years

15. Kenneth McKellar (D-TN)

March 4, 1917 to January 2, 1953

35 years, 10 months

16. Milton Young (R-ND)

March 12, 1945 to January 2, 1981

35 years, 9 months

17. Pete V. Domenici (R-NM)

January 3, 1973 to present

35 years, 8 months

17. Joseph R. Biden, Jr. (D-DE)

January 3, 1973 to present

35 years, 8 months

18. Ellison D. Smith (D-SC)

March 4, 1909 to November 17, 1944

35 years, 8 months

19. Allen J. Ellender (D-LA)

January 3, 1937 to July 27, 1972

35 years, 7 months

20. William B. Allison (R-IA)

March 4, 1873 to August 4, 1908

35 years, 5 months