Sen. Barbara Mikulski is used to making history.

She is the first woman to win statewide office in Maryland, the first female Democrat to serve in both chambers of Congress and the first Democratic woman elected to the Senate “in her own right” — without being appointed or taking the seat after a husband’s death. She will again chart new territory next week.

Once sworn in to the 112th Congress, Mikulski will become the longest-serving female Senator in American history.

The 74-year-old Baltimore native, elected to the Senate in 1986, will begin her fifth term when the 112th Congress begins. In doing so, she will exceed the mark set by former Maine Sen. Margaret Chase Smith, a Republican who served the Pine Tree State for 24 years.

Mikulski, who cruised to a fifth term in November by nearly 25 points, downplayed the achievement in a statement to Roll Call. “For me, it’s not how long you serve, it’s how well you serve,” she said. “The Constitution tells us that Senators are elected to  represent our states. I am first and foremost the Senator from Maryland and the Senator for Maryland. I fight for the people of Maryland — their jobs and their opportunities to succeed — fiercely and unabashedly.”

Known as a proponent for women in politics, Mikulski has traditionally hosted workshops for new female Senators to help them transition into a world long dominated by men. But next year, just one woman, Sen.-elect Kelly Ayotte (R-N.H.), will join the Senate. With the departure of Sen. Blanche Lincoln (D-Ark.), the total number of women in the Senate will remain at 17.

The 2010 midterms offered an unusual storyline for women in politics.

Jennifer Lawless, director of the Women & Politics Institute at American University, notes that while a record number of women ran for Congress (138 in the House and 15 in the Senate), those who will be seated in the new Congress will fall for the first time in three decades. The number of women in the Senate will not change, but female Representatives will drop from 73 to 71.

But Mikulski may offer women some hope, Lawless said. “Barbara Mikulski’s tenure in the U.S. Senate signals to other women — both those who already serve in politics and those who might be interested in entering the electoral arena — that women can win elections, consistently gain re-election and accrue seniority in the chamber,” she said. “Moreover, it suggests that many of the women who were elected several election cycles after Mikulski might be around for a long time, as are many of their male counterparts.”

While Lawless didn’t offer any names, the short list of powerful women in the Senate include California Democratic Sens. Dianne Feinstein and Barbara Boxer (both elected in 1992) and Maine Republican Sens. Olympia Snowe (elected in 1994) and Susan Collins (elected in 1996).

Mikulski’s record also offers another lesson, Lawless said.

“The fact that Mikulski is the only woman to serve longer than 24 years also reinforces the fact that women are still relatively new entrants to the U.S. Senate,” she said. “Given that the bulk of women in Congress were elected in 1992 or later, there have been few opportunities for women to achieve years of service comparable to many of their male colleagues.”

Indeed, the number of female Senators could be counted on one hand until 1993, and on two hands until 2001.

Smith’s early example offers some perspective. The Maine Republican served in the Senate from 1949 to 1973, a tenure spanning more than two decades during which she was usually the only female Member in the chamber.

And when Mikulski joined the Senate, there was just one other woman in the chamber, Sen. Nancy Kassebaum (R-Kansas).

“I was the first Democratic woman elected in my own right, but I didn’t want to be the only. I wanted to be the first of many,” Mikulski said. “I believe in the empowerment of women and work for them to use their power in their community, and to run for a public office. When I first arrived in the Senate, I was the 16th woman in all of American history to serve in the Senate. Today we have 17 women serving in the Senate at one time. That’s a stunning accomplishment.”