Fifty years ago, a clever, determined woman named Kathrine Switzer crossed the finish line at the Boston Marathon - but not before an official tried to drag her from the course.
Switzer wore the familiar bib No. 261 on Monday, the same number she wore in 1967.
Also running on Monday was Ben Beach, who completed the race for an unprecedented 50th time in a row.
Ms Switzer's run 50 years ago is widely credited with forcing the Boston Marathon to start allowing female runners in 1972. It wasn't until the race began that officials noticed a woman running among the men.
Her boyfriend, who was running with her, managed to shove the official out of the way and Ms Switzer kept running.
The accident happened during a routine run in South Portland on July 4th, 2016. "The number now stands for all of those things".
In 1967, Switzer had purposely registered under "K.V. Switzer" so as not to reveal her gender.
Pictures of that splashed across newspaper front pages, and Switzer somewhat inadvertently became a symbol of the women's movement.
Atsede Baysa is back to defend her women's title, but she will be joined in the field by another returning victor fresh off a Boston victory.
A viral Facebook video that has been viewed over 6 million times shows the moment Army Staff Sergeant Earl Granville carried a woman across the finish line on Monday.
"He said, 'No dame ever ran no marathon, '" she said.
According to the New York Times, more than half of marathon runners in the United States are women.
The 38-year-old mother of two broke away from Kenyan-born Rose Chelimo of Bahrain with five kilometres to go to win the race on her debut in 2 hours 21 minutes and 53 seconds.
In the midst of this year's excitement, Granville said he made it to the end before lifting up his friend and marathon guide, Andi Piscopo, 38, of Attleboro, Massachusetts. "This time it was wall-to-wall cheering, and people not just congratulating me, but thanking me". It was a joyous experience. "And I saw that he had not come with me, so I pushed a little bit more".
She went on to run 39 marathons, and achieving her personal best in 1975, 2:51:33, when she finished second in Boston. Americans had six of the top 10 finishers in the men's race and two of the top four women. If I quit, [race manager] Jock Semple and all those like him would win. "I'm my own worst critic, but my critique document is still blank".