Longest Serving US Senators Fast Facts

Chairman Patrick Leahy (D-VT), speaks during a Senate Judiciary Committee hearing on April 22, 2013 in Washington, DC. (Photo by Mark Wilson/Getty Images)

(CNN)Here's a look at the top 25 longest-serving senators in United States history.

The Top Twenty-Five as of 9/15/2016:
Names in bold are currently serving in the US Senate
1) Robert C. Byrd (D-WV), 51 years, 5 months, 26 days
January 3, 1959 to June 28, 2010
    2) Daniel K. Inouye (D-HI), 49 years, 11 months, 14 days
    January 3, 1963 to December 17, 2012
    3) Strom Thurmond (R-SC), 47 years, 5 months, 8 days
    December 14, 1954 to April 4, 1956
    November 7, 1956 to January 3, 2003
    4) Edward M. Kennedy (D-MA), 46 years, 9 months, 19 days
    November 7, 1962 until his death on August 25, 2009
    5) Carl T. Hayden (D-AZ), 41 years, 9 months, 30 days
    March 4, 1927 to January 2, 1969
    6) Patrick Leahy (D-VT), 41 years, 4 months, 22 days as of 9/15/2016
    January 3, 1975 to present
    7) John C. Stennis (D-MS), 41 years, 1 month, 29 days
    November 5, 1947 to January 2, 1989
    8) Theodore F. Stevens (R-AK), 40 years, 10 days
    December 24, 1968 to January 3, 2009
    9) Orrin Hatch (R-UT), 39 years, 4 months, 22 days as of 9/15/2016
    January 3, 1977 to present
    10) Ernest F. Hollings (D-SC), 38 years, 1 month, 25 days
    November 9, 1966 to January 3, 2005
    11) Richard B. Russell (D-GA), 38 years, 10 days
    January 12, 1933 to January 21, 1971
    12) Russell Long (D-LA), 38 years, 3 days
    December 31, 1948 to January 2, 1987
    13) Thad Cochran (R-MS), 37 years, 4 months, 28 days as of 9/15/2016
    December 27, 1978 to present
    14) Francis E. Warren (R-WY), 37 years, 4 days
    November 18, 1890 to March 3, 1893
    March 4, 1895 to November 24, 1929
    15) James O. Eastland (D-MS), 36 years, 2 months, 24 days
    June 30, 1941 to September 28, 1941
    January 3, 1943 to December 27, 1978
    16) Warren Magnuson (D-WA), 36 years, 20 days
    December 14, 1944 to January 2, 1981
    17) Joseph R. Biden, Jr. (D-DE), 36 years, 13 days
    January 3, 1973 to January 20, 2009
    18) Pete V. Domenici (R-NM), 36 years
    January 3, 1973 to January 3, 2009
    18) Richard Lugar (R-IN), 36 years
    January 3, 1977 to January 3, 2013
    18) Claiborne Pell (D-RI), 36 years
    January 3, 1961 to January 3, 1997
    18) Carl Levin (D-MI), 36 years
    January 3, 1979 to January 3, 2015
    22) Kenneth McKellar (D-TN), 35 years, 10 months
    March 4, 1917 to January 2, 1953
    23) Milton R. Young (R-ND), 35 years, 9 months, 22 days
    March 12, 1945 to January 3, 1981
    24) Ellison D. Smith (D-SC), 35 years, 8 months, 13 days
    March 4, 1909 to November 17, 1944
    25) Allen Joseph Ellender (D-LA), 35 years, 6 months, 24 days
    January 3, 1937 to July 27, 1972