Now in her fifth decade of public service, Sen. Barbara Mikulski (D-Md.) has been in office long enough to see many milestones come and go.But the next record she will set may prove the most enduring.

Maryland Gov. Martin J. O' Malley laughs during remarks by Sen. Barbara Mikulski during his inauguration ceremony in Annapolis in January. (Mark Gail/THE WASHINGTON POST)

Mikulski’s Senate colleagues will pay tribute to her on the chamber floor on Wednesday afternoon, and that evening she will be honored at a reception hosted by House Minority Leader Nancy Pelosi (D-Calif.).

Known now as the “dean” of Senate women, Mikulski has been in office long enough to see significant changes come to the Capitol, particularly when it comes to women serving in office.

When Mikulski began her House tenure in 1977, she was one of 21 women serving in Congress — 18 in the House and three in the Senate. Today there are 92 women serving, with 17 in the Senate.

Along the way, she had to battle stereotypes, including some that suggested women couldn’t be serious legislators. When she entered the Senate, she told The Washington Post last year, “I was greeted with a lot of skepticism from my male colleagues.” She added: “Was I going to go the celebrity route or the Senate route? I had to work very hard.”

Among Mikulski’s other “firsts,” as we noted last year: She was the first female Democrat to serve in both chambers of Congress and the first female Democrat to be elected to the Senate without succeeding her husband or father. In the Senate, she was the first woman to chair an Appropriations subcommittee and the first woman to serve on a handful of other panels.

You can also explore a Mikulski photo gallery and a timeline of Mikulski’s career.