Kathrine Switzer will find no impediments in this year’s Boston Marathon. (AP)

This time, the woman wearing Boston Marathon Bib No. 261 left her hotel Monday morning and was greeted with smiles, knowing that she need not worry that an overzealous race official might try to take her off the course. Now, 50 years after when Kathrine Switzer became the first woman to officially run the marathon — a milestone nearly derailed by an ugly moment — she returns a hero of women’s running.

“No dame ever ran the Boston Marathon,” she recalled Arnie Briggs, her coach at Syracuse, telling her in her memoir, “Marathon Woman.”

Although Bobbi Gibb had run the race in 1966, she did so without a bib. Switzer entered as “K.B. Switzer” and Jock Semple, the race director, became part of history when he realized that a woman was running and photographers captured images of him trying to keep her off the course. “Instinctively I jerked my head around quickly and looked square into the most vicious face I’d ever seen,” she wrote in her memoir. “A big man, a huge man, with bared teeth was set to pounce, and before I could react he grabbed my shoulder and flung me back, screaming, ‘Get the hell out of my race and give me those numbers!’”

She finished the race and became one of the faces of women’s running. “Everything changed,” Switzer, 70, told WBZ. “I said, ‘This is going to change my life, maybe going to change women’s sports and change the world.’”

Until Monday, she hadn’t run the race since 1976, preferring instead to be part of TV coverage. Now Switzer, wearing the No. 261 that the Boston Athletic Association will officially retire, is back and she won’t be alone. Since 2010, Running USA reports that female finishers annually have outnumbered males at all U.S. running events combined.