Sen. Barbara Mikulski (D-Md.) is expected to announce her retirement on Monday, declining to seek her sixth term in the United States Senate. She'll leave office as the longest-serving woman in the history of Congress. But that record will probably be broken fairly quickly.

Using data from GovTrack, we calculated the longest-serving members of Congress. Mikulski's record tenure is clear when you look at the rankings of female members of Congress. (This combines House and Senate service; Mikulski got to the Senate in 1987.)

But notice how many of the women who trail her are currently serving. Only the light-colored bars are those who will be retired at the end of this term. The closest (who isn't retiring in 2016) is Marcy Kaptur, who, at 68 years old, could certainly serve the additional eight years it would take to depose Mikulski. (Mikulski will be 79 next year.)

Mikulski's 38 years on Capitol Hill is remarkable -- though somewhat shorter than the all-time tenure record, held by John Dingell, who served over 59 years. In fact, Mikulski is only ninth on the list of longest-serving members among those who are currently in Congress, a function of the far higher number of men in Congress, particularly 40 years ago.