In 1967, Kathrine Switzer made history by becoming the first woman to officially enter the Boston Marathon.
She entered with her initials K.V. Switzer, and said there were no official rules saying only men could enter the race.
She competed as a 20 year old journalism student, and was attacked by her fellow runners who took offence to her competing.
She was photographed in an iconic image:
Although she wasn't the first to compete (Roberta Bingay Gibb completed the Boston Marathon in 1966 without a bib), she was the first to finish the race having officially entered it.
On Monday, she finished her 40th marathon, her ninth time on the Boston course. She finished in 4:44:31.
After the race, she told CNN via a phone interview:
What happened on the streets of Boston 50 years ago completely changed my life and changed other people's lives.
The race today was a celebration of the past 50 years; the next 50 are going to be even better.