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 2/9/2017:
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-June 28, 2010
2) Daniel K. Inouye (D-HI), 49 years, 11 months, 14 days
January 3, 1963-December 17, 2012
3) Strom Thurmond (R-SC), 47 years, 5 months, 8 days
December 14, 1954-April 4, 1956 and November 7, 1956-January 3, 2003
4) Edward M. Kennedy (D-MA), 46 years, 9 months, 19 days
November 7, 1962-his death on August 25, 2009
5) Patrick Leahy (D-VT), 42 years, 1 month, 6 days
January 3, 1975-present
6) Carl T. Hayden (D-AZ), 41 years, 9 months, 30 days
March 4, 1927-January 2, 1969
7) John C. Stennis (D-MS), 41 years, 1 month, 29 days
November 5, 1947-January 2, 1989
8) Orrin Hatch (R-UT), 40 years, 1 month, 6 days
January 3, 1977-present
9) Theodore F. Stevens (R-AK), 40 years, 10 days
December 24, 1968-January 3, 2009
10) Ernest F. Hollings (D-SC), 38 years, 1 month, 25 days
November 9, 1966-January 3, 2005
11) Richard B. Russell (D-GA), 38 years, 10 days
January 12, 1933-January 21, 1971
12) Thad Cochran (R-MS), 38 years, 1 month, 13 days
December 27, 1978-present
13) Russell Long (D-LA), 38 years, 3 days
December 31, 1948-January 2, 1987
14) Francis E. Warren (R-WY), 37 years, 4 days
November 18, 1890 to March 3, 1893
March 4, 1895-November 24, 1929
15) James O. Eastland (D-MS), 36 years, 2 months, 24 days
June 30, 1941-September 28, 1941 and January 3, 1943-December 27, 1978
16) Warren Magnuson (D-WA), 36 years, 20 days
December 14, 1944-January 2, 1981
17) Joe Biden (D-DE), 36 years, 13 days
January 3, 1973-January 20, 2009
18) Charles E. Grassley (R-IA), 36 years, 1 month, 6 days
January 3, 1981-present
19) Pete V. Domenici (R-NM), 36 years
January 3, 1973-January 3, 2009
19) Carl Levin (D-MI), 36 years
January 3, 1979-January 3, 2015
19) Richard Lugar (R-IN), 36 years
January 3, 1977-January 3, 2013
19) Claiborne Pell (D-RI), 36 years
January 3, 1961-January 3, 1997
23) Kenneth McKellar (D-TN), 35 years, 10 months
March 4, 1917-January 2, 1953
24) Milton R. Young (R-ND), 35 years, 9 months, 22 days
March 12, 1945-January 3, 1981
25) Ellison D. Smith (D-SC), 35 years, 8 months, 13 days
March 4, 1909-November 17, 1944