Washington (CNN) -- Barbara Mikulski remembers what a man's world the Senate was when she arrived 24 years ago.
"There's this place called the Senate gym. The locker room," Mikulski says, slowly and emphatically for effect.
"They just couldn't accommodate me and I'm not much of a jock anyway, but that's where they networked and that's where they bonded," Mikulski says, speaking of her male Senate colleagues.
When she arrived in 1986, Mikulski was one of only two women in the Senate. She was the first Democratic woman elected to the Senate in her own right.
"Other women had served in the Senate, but they had succeeded the unexpired term. They usually had a husband who passed away," she recalls.
When she is sworn in for a fifth term in January, Mikulski will become the longest serving woman in Senate history, breaking the 24-year record held by the late GOP Sen. Margaret Chase Smith of Maine.
To mark her milestone, Mikulski invited CNN to her Senate office for an interview to reflect on her tenure -- especially her efforts to empower other women.
Some of the barriers she has broken now seem quite unusual.
For example, Mikulski says that when she arrived in the Senate, what she wore become a "very big deal."
"I'm most comfortable wearing slacks, and well, for a woman to come on the (Senate) floor in trousers was viewed as a seismographic event," says Mikulski.
She said she had to alert Sen. Robert Byrd, D-West Virginia, then the Democratic leader, that she intended to wear pants to work.
"The Senate parliamentarian had looked at the rules to see if it was OK. So, I walk on that day and you would have thought I was walking on the moon. It caused a big stir," she remembers with a mischievous smile.
The 74-year-old Mikulski did not always aspire to be in public service. As a young girl growing up in Baltimore, she dreamed of being like famed scientist Madame Curie. But she went on to become a social worker.
It was a late 1960s fight to stop a proposed highway from tearing up the historic Fells Point neighborhood in Baltimore that whetted Mikulski's political appetite.
After she won that battle, Mikulski ran for a seat on City Council, and in 1976 she launched a successful bid for the U.S. House of Representatives.
In 1986 she became the first woman elected to statewide office in Maryland, and when she arrived in the Senate, she quickly racked up a lot of firsts: The first woman to sit on the powerful Senate Appropriations Committee, the first Democratic woman elected to Senate leadership, and more.
Since Mikulski didn't have other women to help her along, she sought out male mentors, like her senior senator from Maryland, Paul Sarbanes, and the late Sen. Ted Kennedy, D-Massachusetts.
She said her goal was never to be one of the boys, but "one of the gang," and it was clear she would have to work twice as hard as the men and be tough as nails.
"The way you get to be one of the gang in the Senate is by doing your homework, participating in the activities of the Senate, having a great sense of humor and be willing to duke it out when you have to," Mikulski says.
In 1992, known as the "Year of the Woman," four new female Democrats were elected to the Senate, and Mikulski says she felt a weight lifting off her shoulders.
"When I served all by myself, I felt that a lot of the responsibility -- and a lot of the mail that women write, they write us with their personal problems from all over America about their issues on child support, their issues on trying to be able to find a job, their issues on how to be able to adopt a child, there were lots of things -- and when my fellow sisters came, they were able to help me," she recalls.
Mikulski took it upon herself to organize seminars for new female senators and show them the ropes, something she still does for women elected to the Senate from both parties.
"You know, there is no training program when you arrive here. Usually it's been every man for himself, but I was going to be every woman -- each one teach one. So I organized a power workshop. The media said 'Are you having tea?' and I said 'No, it's about power.' "
She is now known as the dean of Senate women.
"I take that very seriously. I see that it's my job to be able to organize the women in a way where their talents are served," Mikulski says.
She says she thinks female senators bring insight to issues relating to women and family that male senators may not.
"While we work on the macro issues, we want to make sure the macaroni-and-cheese issues are at the table, and we speak for them," Mikulski says, speaking of women in America.
Mikulski, who has always won her Senate bids with at least 60% of the vote, is careful to make clear that her responsibilities go well beyond women's issues.
The senator who had wanted to be Madame Curie says one of her greatest achievements is helping to save the budget for the Hubble telescope.
"It's one of my proudest accomplishments in the Senate that we have the Hubble telescope and that it reveals so much knowledge in science, in the development of technology," she says, standing in front of a large framed image of space taken from the Hubble.
"Science and technology is my passion. I believe it can change the world, transform the world, and even save the world," she says.
Still, Mikulski is even more eager to show off a pen displayed in her office -- the first pen President Obama used to sign his first piece of legislation into law. It was a bill Mikulski had pushed through the Senate to give women equal pay for equal work.
"It righted a wrong. Women should have equal pay for comparable work," Mikulski says. "To have Barack Obama (sign it) as his very first piece of legislation -- it very much was a three-Kleenex affair for me."
Other prize possessions around her office are pictures with fellow female senators. There are now 17, and they still meet monthly for off-the-record dinners, which Mikulski organizes.
In fact, in these polarizing political times, the dinners are one of the last bastions of bipartisanship.
"It's a very important way for us to know each other as people," she says.
Despite partisan differences, Mikulski has used the dinners to help the female senators forge relationships, which she says help them understand each other across party and regional lines when it comes to policy.
"We do know each other and we have developed real affection and respect for one another," she says.
Women still only make up 17% of the Senate, despite making up more than 50% of the population. In the next Congress, for the first time in three decades, the number of women serving will not go up.
Still, the woman poised to become the longest-serving female senator stands in front of one of the photographs of the group of 17, and notes that there are more women in the picture than had served in all of American history when she arrived 24 years ago.
"This is a stunning accomplishment," she says.
CNN's Lesa Jansen contributed to this report.