Boston Marathon bib number 261 has been imbued with meaning since Kathrine Switzer wore it in 1967, when she became the first woman to be officially registered and run in the race.
Now, the same year that the trailblazing Switzer is again running in the Boston Marathon, the number will be officially retired.
The Boston Athletic Association announced the honor on Thursday. It is a long way from Switzer's first run 50 years ago, when an angry race official attempted to rip the number off her shirt.
Switzer had registered for the marathon not with her first name but with her initials, which kept her gender hidden from marathon officials.
Women were not allowed to run in the Boston Marathon then, and weren’t officially allowed into the race until 1972.
Switzer wasn’t technically the first woman to run the Boston Marathon, however. Roberta Gibb had run the race secretly the year before without an official number.
This year, Switzer will run in Monday's event to mark the 50th anniversary of her pioneering race. Now 70, she completed 39 marathons since that run in Boston, and also started an organization called 261 Fearless, a nonprofit that brings together women runners.
This year is the 121st Boston Marathon, and in its history, the association has only retired one other number, according to the Associated Press.
That was number 61, honor long-distance runner John Kelley, who ran 61 Boston Marathons.