Bobbi Gibb running the 1967 Boston Marathon. The year prior, she became the first woman to finish the race. Photo: The Boston Globe/Getty Images

On April 19, 1966, a 23-year-old woman in a blue hoodie hid in forsythia bushes near the start of the Boston Marathon. After the gun fired and half the pack passed, she jumped into the race wearing a swimsuit, her brother’s Bermuda shorts, and boy’s shoes.

Entering a race without paying is a giant no-no in the running world, but Roberta “Bobbi” Gibb ran as a bandit in protest of the Boston Athletic Association’s ban on women participants.

When she wrote to request an entry that winter, B.A.A. officials replied that Amateur Athletic Union regulations “forbid women to compete in any race longer than 1.5 miles,” plus, “women are physiologically incapable of running 26.2 miles.” She’d been training since the 1964 race and was now even more motivated to run.

“It dawned on me that if I could run Boston, I could erase other false beliefs about women’s limitations,” she told the New York Times. Gibb ran much of the race in fear that she’d be arrested, but she finished without incident in 3:21:40, ahead of two-thirds of the male field.

She ran the race the following two years but wasn’t recognized as the women’s winner until the race’s 100th anniversary in 1996. (In 1967, Kathrine Switzer did successfully register for the race using the initials K.V. Switzer, though ticked-off race director Jock Semple tried to yank her out around mile four. Switzer finished in 4:20:02.) The Boston Marathon didn’t technically allow women to enter until 1972, two months before Title IX passed.

Though athletes like Gibb and Switzer proved that women were more than capable of running 26.2 miles, it took years for the highest level of sports to catch up. The longest distance women could compete in through the 1980 Games was 1500 meters, or just shy of a mile. Some say it was Switzer’s involvement with the Avon International Running Circuit of women’s-only races that helped sway the International Olympic Committee to include the women’s marathon (and 3,000 meters) at the 1984 Games in Los Angeles.

Women have fueled what’s known as the Second Running Boom starting in the mid ’90s, and their participation in distance running is astounding when you consider the not-so-distant past. In 2013, women accounted for 43 percent of all marathon finishers and made up 61 percent of all half-marathoners.

Bobbi Gibb may not always get her due, but today, she served as grand marshal of the country’s most prestigious marathon, where more than 13,000 women had entered. They wouldn’t be there without her.