Which U.S. Senator holds the record for the longest continuous term in office?

Robert "Bob" Byrd (born Cornelius Calvin Sale, Jr., November 20, 1917 – June 28, 2010) was a United States Senator from West Virginia. A member of the Democratic Party, Byrd served as a U.S. Representative from 1953 until 1959 and as a U.S. Senator from 1959 to 2010. He holds the record for serving the longest continuous term in office as a United States Senator. His total tenure was 51 years, 176 days.

He is remembered by many Americans because he filibustered against the 1964 Civil Rights Act and supported the Vietnam War, but later backed civil rights measures and criticized the Iraq War. Also, known for his knowledge of U.S. Senate precedent and parliamentary procedure, Senator Byrd during the later part of his life wrote a four volume history of the Senate. This work is seen by experts as a very insightful treatise.