In her original run, as part of the Syracuse Harriers athletics club, Switzer made worldwide headlines after race official Jock Semple broke into the runners to rip the number off her sweatshirt.
In 1963 two women crashed the Western Hemisphere Marathon in Culver City, Calif., and one finished.
On Monday, Switzer, now 70, ran the Boston race for the ninth time, finishing under the qualifying time at 4 hours, 44 minutes and 31 seconds with an average mile of 10:51, according to CNN.
This time, she was far from the only woman.
Shortly after the marathon, Boston Athletic Association director Will Cloney was asked to offer his opinion on a female runner registering and completing the historically male race.
Writing on Facebook after the race, Ms Switzer said: "I finished, like I did 50 years ago". In fact, the received wisdom was that running would rob women of their only attribute - that they could breed - and if a delicate flower was to so much jog to the bus stop her womb might fall out.
Marine Staff Sgt. Jose Luis Sanchez, who lost the lower part of his left leg after he stepped on an IED in Afghanistan, ran while carrying an American flag signed by many who served with him in Afghanistan. "They would just think that I was a clown, and that women were barging into events where they had no ability".
Before the race, Switzer spoke with NPR about the day she made history. Women were officially allowed to enter the Boston Marathon five years later in 1972, and the Olympics in 1984.
"He said, 'No dame ever ran no marathon, '" she said. "We have come a light year, really", she said.
Jimmy Golen has covered the Boston Marathon for The Associated Press since 1995.
Semple couldn't knock Switzer off the course, but he did change her path: After the pictures of the scuffle were splashed across newspaper front pages, she found herself an unintended - but eager - spokeswomen for her gender.