Sen. Barbara Boxer (D-Calif.). (Win McNamee/Getty Images)

When Barbara Boxer (D-Calif.) leaves the Senate at the end of her term in 2016, she will bring to end a streak that set a record in California: the longest tenure during which the same two senators represented the state. Boxer and her Sen. Dianne Feinstein (D) will have served together for 24 years, ever since Boxer was first elected in 1992.

That's a long time for two people to work in tandem, in the abstract -- particularly in 2015. But in the scale of the Senate, where people have near-guaranteed jobs for six years and incumbents usually win reelection, it's not long at all.

According to our analysis of data from GovTrack, the longest-serving duo in Senate history was South Carolina's Strom Thurmond (D, then R) and Fritz Hollings (D). They served together for 37 years, until Thurmond's retirement at age 100. He spent more than one-third of his life on Capitol Hill alongside Hollings.

A number of states, in fact, have had senator teams last about 24 years. Which makes sense: One serves four terms, the other five, and you have overlap.

The longest serving pairs from each state

South Carolina J. Thurmond (1955-2003) and Ernest Hollings (1966-2005) 37 years
Mississippi John Stennis (1947-1989) and James Eastland (1941-1979) 32 years
Maine Eugene Hale (1881-1912) and William Frye (1881-1912) 30 years
Arkansas John McClellan (1943-1978) and James Fulbright (1945-1975) 30 years
Iowa Thomas Harkin (1985-2015) and Charles Grassley (1981-?) 30 years
Delaware William Roth (1971-2001) and Joseph Biden (1973-2009) 28 years
Washington Henry Jackson (1953-1984) and Warren Magnuson (1944-1981) 28 years
North Carolina Furnifold Simmons (1901-1932) and Lee Overman (1903-1932) 27 years
Oregon Mark Hatfield (1967-1997) and Robert Packwood (1969-1996) 27 years
West Virginia Robert Byrd (1959-2011) and Jennings Randolph (1958-1985) 26 years
New Mexico Jeff Bingaman (1983-2013) and Pete Domenici (1973-2010) 26 years
California Dianne Feinstein (1992-?) and Barbara Boxer (1993-2017) 24 years
Massachusetts Edward Kennedy (1962-2010) and John Kerry (1985-2014) 24 years
Georgia Richard Russell (1933-1972) and Walter George (1922-1957) 24 years
Connecticut Joseph Hawley (1881-1906) and Orville Platt (1879-1906) 24 years
Vermont George Edmunds (1866-1892) and Justin Morrill (1867-1900) 24 years
Louisiana Allen Ellender (1937-1973) and Russell Long (1948-1987) 24 years
Missouri Francis Cockrell (1875-1906) and George Vest (1879-1904) 24 years
Alabama John Sparkman (1946-1979) and Joseph Hill (1938-1969) 23 years
Wyoming Clarence Clark (1895-1918) and Francis Warren (1890-1930) 22 years
Hawaii Daniel Akaka (1990-2014) and Daniel Inouye (1963-2013) 22 years
Alaska Ted Stevens (1968-2010) and Frank Murkowski (1981-2003) 22 years
Rhode Island John Chafee (1976-2000) and Claiborne Pell (1961-1997) 21 years
Nebraska Roman Hruska (1954-1977) and Carl Curtis (1955-1979) 21 years
North Dakota Quentin Burdick (1960-1993) and Milton Young (1945-1981) 21 years
New Jersey Harrison Williams (1959-1983) and Clifford Case (1955-1979) 20 years
Maryland Paul Sarbanes (1977-2007) and Barbara Mikulski (1987-?) 20 years
Virginia Harry Byrd (1933-1965) and Absalom Robertson (1946-1967) 19 years
Ohio Howard Metzenbaum (1974-1995) and John Glenn (1974-1999) 19 years
Florida Park Trammell (1917-1937) and Duncan Fletcher (1909-1937) 19 years
New York Daniel Moynihan (1977-2001) and Alfonse D'Amato (1981-1999) 18 years
Wisconsin William Proxmire (1957-1989) and Gaylord Nelson (1963-1981) 18 years
Kansas Nancy Kassebaum (1978-1997) and Robert Dole (1969-1997) 18 years
Montana Conrad Burns (1989-2007) and Max Baucus (1978-2014) 18 years
Utah Orrin Hatch (1977-?) and Robert Bennett (1993-2011) 18 years
Arizona Jon Kyl (1995-2014) and John McCain (1987-?) 18 years
Illinois Paul Douglas (1949-1967) and Everett Dirksen (1951-1969) 16 years
Michigan Donald Riegle (1976-1995) and Carl Levin (1979-2015) 16 years
Minnesota Moses Clapp (1901-1918) and Knute Nelson (1895-1924) 16 years
Nevada William Stewart (1864-1906) and John Jones (1873-1904) 16 years
Oklahoma Robert Owen (1907-1926) and Thomas Gore (1907-1937) 15 years
Kentucky Mitch McConnell (1985-?) and Wendell Ford (1974-1999) 14 years
New Hampshire Henry Keyes (1919-1937) and George Moses (1918-1934) 14 years
Indiana Rupert Hartke (1959-1977) and Birch Bayh (1963-1981) 14 years
Texas Lloyd Bentsen (1971-1994) and John Tower (1961-1985) 14 years
Colorado Edwin Johnson (1937-1955) and Eugene Millikin (1941-1957) 14 years
Tennessee* Bob Corker (2007-?) and Lamar Alexander (2003-?) 12 years
Pennsylvania Richard Santorum (1995-2007) and Arlen Specter (1981-2011) 12 years
South Dakota Karl Mundt (1948-1973) and Francis Case (1951-1963) 11 years
Idaho Leonard Jordan (1962-1973) and Frank Church (1957-1981) 11 years

* This assumes both senators from Tennessee will complete their current terms. The state has had an unusual number of overlapping / short-term senators.

What currently serving duo could match Hollings and Thurmond? With Boxer leaving, the runners-up are Sens. Jeff Sessions and Richard Shelby of Alabama, who've worked together since 1997. That's 18 years -- meaning they'd need to serve together until 2035 to topple the South Carolinians. (Shelby, like Thurmond, would be 100 years old.) But in only five more years, they'll seize the record in their state.

For Boxer, that in-state record will have to suffice.