One brisk morning in early 1993, Carol Moseley-Braun selected a favorite pantsuit from her closet and went off to her new job in Washington, D.C. The Democrat, who had previously served in the Illinois state Senate for a decade, had been elected in November 1992 on a platform of women's rights and civil rights. When she won, she replaced incumbent Democratic Senator Alan Dixon and became the first African-American woman to serve as a United States senator. But when she set foot on the Senate floor that winter day, wearing "my nice outfit," as she said later, "the gasps were audible." Unbeknownst to Moseley-Braun—who had donned pantsuits frequently during her time in the Illinois legislature—women were forbidden from wearing pants on the Senate floor.

She had broken a rule, albeit an unwritten one. It was enforced by peer pressure and official Senate doorkeepers who could turn away anyone they didn't think looked "appropriate," and it remained an important fact of daily life among women in the Senate for decades. That is, until Moseley-Braun and another political pioneer intervened to challenge it.

Carol Moseley-Braun declaring victory in November 1992. Image credit: Getty Images

Like other gentlemen of their day,

early senators wore waistcoats, frock coats, and breeches with stockings—nothing too fancy, since ostentatious clothing had a whiff of aristocracy about it. But by the late 19th century, senators were dressing in formal clothes, complete with vests, cutaway coats, and striped trousers. Fashion was generally consistent despite some regional differences, and experienced senators policed newer members, ensuring they were dressed to preserve the dignity of the legislative chamber.

When women first began entering Congress—starting when Jeannette Rankin was elected to the House of Representatives in 1916—they dressed in dark colors and conservative cuts to avoid drawing attention to themselves. In the 1940s, once women began serving in the House in larger numbers, Reps. Mary Norton (a Democrat from New Jersey) and Frances Bolton (a Republican from Ohio) would patrol the fashion choices of other female representatives. The historian for the House of Representatives, Matthew Wasniewski, told The Hill in 2011 that "If [congresswomen] were wearing a dress that Norton considered too frilly, she would go up and say something to them."

Trousers became common leisurewear for women by the mid-20th century, but it took a while longer before women wore pants to the office or on formal occasions. Slacks and pantsuits only began entering the mainstream of acceptable workwear for women around 1970, when they were first allowed at federal agencies, including the State Department and the Pentagon—though they were still forbidden at the FBI until after J. Edgar Hoover died in 1972; he hated seeing women in pants.

That year, Pat Nixon wore two pantsuits by American designers in a fashion spread, becoming the first sitting first lady to be photographed publicly wearing trousers. Around the same time, fashion norms started to change in the House of Representatives: Rep. Charlotte T. Reid, a Republican from Illinois, made history in 1969 when she showed up to the House in a "black wool, bell-bottomed pantsuit … a first in the annals of the U.S. Congress." One male colleague couldn’t believe it, remarking to Reid, "I was told there was a lady here in trousers, so I had to come over and see for myself."

Women of the 89th Congress, 1965, with Charlotte Reid standing at far right. Image credit: Wikimedia Commons // Public Domain

In the Senate, norms were harder to change.

As the upper house in the U.S. legislature, the Senate has always been more formal and reserved than the House. Even during the 1980s, pants on women were apparently too much for that august chamber to handle. Individual Senate offices had their own rules, but on the floor, women wearing pants were verboten, which could necessitate quick changes. "We've heard from women staff that in the 1980s, if they came in to work—if they were called in on an emergency basis—they needed to keep a dress to put on quickly or they had to borrow one if they had to appear on the Senate floor," Richard A. Baker, Senate historian from 1975 to 2009, told The Washington Post in 2002.

While the dress code for the Senate was never officially codified, the norms were enforced by Senate doorkeepers, who controlled access to the chamber and served partly as security guards, partly as protocol monitors. Even today, they assess each person seeking entry, making sure they are supposed to be there and are dressed appropriately. The problem is that "dressed appropriately" has historically been up to the discretion of the doorkeeper on duty: Doorkeepers made determinations based on personal opinion or instructions from their boss, the sergeant at arms.

In 1972, a group of female Senate aides wrote a letter to the chairman of the rules committee, complaining that each doorkeeper had his own fashion requirements and asking that a written dress code be developed so they’d know when their outfits were acceptable. "It's just so silly," one aide told the Los Angeles Times. “You just don’t have the time to second-guess the sergeant-at-arms at 8 in the morning when you’re trying to get dressed.” The rules committee apparently ignored their request.

Sens. Patty Murray, Barbara Mikulski, Barbara Boxer, Carol Moseley-Braun, and Diane Feinstein in 1992. Image credit: Wikimedia Commons // Public domain

In 1993, the gender balance in the Senate

finally started to shift. Until that year, only two women senators had ever served simultaneously. But in November 1992, four women won Senate seats, joining Nancy Kassebaum (a Republican from Kansas first elected in 1978) and Barbara Mikulski (a Democrat from Maryland first elected in 1986) for a total of six women—the largest-yet group of female legislators in the upper house.

One of those new senators was Moseley-Braun. During her years in the Illinois state legislature, she’d grown accustomed to wearing pantsuits, and when she joined the U.S. Senate, she was unaware they weren’t allowed. "It was one of those unwritten rules that they don’t tell you about unless you're part of the circle," she said recently in an interview with WBEZ. "And nobody was talking to me about these things, so I had no clue."

On that winter day in 1993, after hearing the gasps from the men in chamber, Moseley-Braun recalled that she'd wondered, "'What’s up? What’s the problem?' It’s not like I had on a kilt." The senator didn't realize what she'd done until female staffers came up to thank her. They'd been fighting for the right to wear pants for years, and now they had a senator on their side.

Barbara Mikulski and other women Democratic senators at the 2004 Democratic National Convention. Image credit: Getty Images.

Actually, they had two.

Around the time Moseley-Braun was inadvertently bucking the no-pantsuit rule, Sen. Barbara Mikulski had made up her mind to challenge the same outdated norm. "It was a snowy day" sometime in early 1993, she told Vice, "and I found out more bad weather was coming. I just really wanted to be comfortable. I'm most comfortable wearing slacks."

Unlike Moseley-Braun, Mikulski knew she was breaking a long-standing tradition, so she approached fellow Democrat Robert Byrd, then the President pro tempore of the Senate, to advise him of her plans to wear pants. Byrd had the Senate parliamentarian, Alan Frumin, check the rules to make sure pants on women weren’t explicitly outlawed. When he determined that they weren't, Byrd "gave the nod," Mikulski remembered. "He didn't say yes, but he gave a nod." Soon Mikulski was walking onto the Senate floor in a pair of slacks, and from the reaction, she recalled, "You would have thought that I was walking on the moon." (While there are no official Senate records showing which woman wore pants on the Senate floor first, newspaper accounts suggest Mikulski's act followed Moseley-Braun's.)

The pants-wearing senators had set a precedent—one that would soon become permanent. The Senate sergeant at arms that year was Martha Pope, the first-ever woman to hold the job (she had been elected two years prior). According to the Chicago Sun-Times, her doorkeepers followed a written policy manual that stated, "Women are required to wear business attire, i.e., dress, skirt and blouse or business suit." After Moseley-Braun and Mikulski wore pantsuits on the floor, Pope circulated a memo to her staff, amending the manual to read, "Women are required to wear business attire, i.e. dress, skirt/blouse, business suit, coordinated pantsuit (slacks and matching blazer; no stirrup pants)."

Sen. Barbara Mikulsk on her way to the Senate floor in 2014. Image credit: Getty Images

Senator Diane Feinstein joined her colleagues in wearing pantsuits from time to time, and female staffers and journalists took advantage of this new freedom as well. Female Senate aides also had a new line of argument for pantsuit-averse supervisors. According to Moseley-Braun, "What happened next was that other people started wearing pants. All the women staffers went to their bosses and said, 'If this senator can wear pants, then why can't I?' And so it was the pantsuit revolution."

Additional Sources: "Women Aides Are Upset: Fashion Furor in the Capital," Los Angeles Times; "Women Now Can Wear the Pants in the Senate," Chicago Sun-Times