( CNN ) -- Rep. John Dingell of Michigan became the longest-serving member of Congress on Friday with 57 years , five months , 27 days and counting on Capitol Hill . His longevity record eclipses that of the late Sen. Robert Byrd of West Virginia . Here 's a look at congressional tenure , by the numbers : . 9.1 years : Average length of service in the United States House of Representatives as of January 2013 , according to the Congressional Research Service . 10.2 years : Average length of service in the U.S. Senate as of January 2013 . 13.4 years : Peak average length of service in the House in the 111th Congress ( 2009-2010 ) . 37 : Percent of congressmen in the 113th Congress that have between 0 and 8 years of experience . 20 , 11 : Average percentage of members of Congress who have n't sought re-election , in the 20th and 21st centuries . 51 years , 5 months , 26 days : Length of time Robert Byrd , D-West Virginia , served in the Senate -- January 3 , 1959-June 28 , 2010 . 6 years : Length of time Byrd served in the House -- January 3 , 1953-January 3 , 1959 . 57 years , 5 months , 27 days : Length of time Rep. John Dingell , Jr. , D-Michigan , has served in the House -- December 13 , 1955-present . 22 years 6 months 17 days : Length of time his father , Rep. John Dingell Sr. , served in the House -- March 3 , 1933-September 19-1955 . 38 years 5 months , 5 days : Length of service for Sen. Patrick Leahy , D-Vermont , the longest currently serving senator -- January 3 , 1975-present . 60 days : Term of former Sen. Dean Barkley , D-Minnesota . He was appointed to the seat of Sen. Paul Wellstone , who was killed in a plane crash in 2002 . 36 years , 5 months , 5 days : Length of congressional service for Sen. Barbara Mikulski , D-Maryland , longest-serving female . She served five terms in the House and is in her fifth term in the Senate -- January 3 , 1977-January 3 , 1987 , in the House ; January 3 , 1987-present in the Senate . 25 : Times John Conyers , D-Michigan , has been elected to Congress . He is the longest-serving African-American in congressional history . Conyers was first elected in 1964 . 51 : Senators in the 113th Congress who had previously served in the House .
Rep. John Dingell became longest-serving member of Congress on Friday . Dingell 's record eclipses that of former Sen. Robert Byrd of West Virginia . Contrast that with the 60 days that Dean Barkley served to finish Paul Wellstone 's term . Dingell and his father , John Dingell Sr. , served a total of 80 years in Congress .