The first women to run the Boston Marathon were chased by organizers of the event!

Katherine Switzer had registered for the Boston Marathon used the name K. V. Switzer to sign up for the marathon. She was used to abbreviating her first name because she used K.V. Switzer to sign the articles she wrote for a college newspaper. 

Because of this abbreviation organizers didn’t realize she was a woman, and so allowed her to register. This was a mistake because, at the time, women were not allowed to run the Boston Marathon. The organizers only realized the mistake when Switzer began running the race. Because she was wearing a number, it was clear that she was registered. 

Alternatively, Bobbi Gibb, another woman, also ran, but she ran unregistered. Jock Semple pursued Switzer, who was running with her boyfriend. He is recorded as having said: "Get the hell out of my race and give me those numbers." 

When Semple got close, Switzer’s boyfriend pushed him out of the way and sent him flying. The picture of Semple being pushed became infamous. It wasn’t until 1972 when women were officially allowed to compete in the Boston Marathon.

(Source)