BOSTON (CBS) -- It was just 50 years ago that women still weren't allowed to run marathons. Kathrine Switzer thought that was silly.
A journalism student at Syracuse at the time, she entered the 1967 Boston Marathon under her initials -- K.V. Switzer, and was given bib No. 261.
But becoming the first woman to officially run the Boston Marathon was not going to be a walk in the park.
"It was a life changing incident. Everything changed," she recently told WBZ-TV's Lisa Hughes. "I said, 'This is going to change my life, maybe going to change women's sports and change the world.'"
The world was indeed changing that afternoon, and Switzer was a part of it. It started when she first crossed the start line in Hopkinton, and then took an odd and unforgettable turn just two miles down the road in Ashland.
"I heard these shoes behind me," she recalled. "I turned and there was Jock Semple. He pounced on me and said, 'Get the hell out of my race! Give me those numbers!' He pushed me and tried to rip my numbers off."
Switzer managed to escape the then-race director with the help of her boyfriend. It was a jarring altercation, one that almost led her to drop out. But she didn't, and continued her run towards history.
It was over those next 24 miles that Switzer realized that she had found her purpose.
"Why aren't other women here? I realized they were afraid and didn't have the opportunities, and I wanted to create those opportunities for them," she said.
And she did. She was the driving force behind the Avon Women's Road Race Series, the first Women's Olympic Marathon in 1984, and she was there when women were finally allowed to run Boston in 1972.
No one was more surprised than Switzer to realize that the 261 bib she wore that day in 1967 -- the one that Semple couldn't wrestle away from her -- had become a symbol to women all over the world.
"At first I thought 261 was just digits. When I heard the stories, saw pictures -- pictures of tattoos ... those are forever. It is forever," she said.
The story behind 261 is Switzer's story itself. It gives other women energy and empowerment.
Four years ago, Edith Zuschmann started a running club where she lives in Austria, and named it "261 Fearless." That marked the birth of a movement.
There are now 261 Fearless clubs all over the world, communities of women focused on only on running, but staying active to stay healthy.
"It's not about becoming faster or becoming a better athlete," said Edith Zuschmann. "It's about just enjoying being active, to stay fit and stay healthy."
But it's more than just running for this pioneer.
"My goal is to reach women in places right now where they're not allowed to leave the house alone, drive a car or get an education," said Switzer. "If running can give them a sense of strength, where they are no longer victims and vunerable, that's what I hope it can do."
It was 50 years ago that they tried to throw Kathrine Switzer out of the race. On Monday, she will lead a group of 125 runners representing 261 Fearless, and she will be celebrated from Hopkinton to Boylston Street.
"Now that she's getting into her later years, you'd think she'd sit back and say, 'I've done my part.' But now I think 261 Fearless is going to be her biggest achievement," said runner Rosy Spraker.
"Running my 50th anniversary, I'm very lucky that physically I can undertake it. It is going to be a joyful celebration," said Switzer, whose 261 became just the second number to be retired on Thursday.
There are currently 26 different 261 Fearless clubs around the world, including two in the Boston area. Click here for more information.
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