In a St. Louis suburb, they chanted, “Hold your burgers, hold your fries. Keep your hands off my thighs.” In Chicago, they had blue duct tape that said “MeToo” covering their mouths. And in Kansas City, Mo., they held signs bearing the same anti-sexual harassment hashtag with the first letter styled to look like the McDonald’s golden arches.

In what organizers said was the first strike in more than 100 years to protest sexual harassment in the workplace, hundreds of McDonald’s employees in those cities and seven others rallied to demand that the largest fast food chain in the country do more to combat the problem.

“We’re protesting today and this is more important than work,” said Kimberly Lawson, explaining that she was skipping her shift to take part in the Kansas City rally. Ms. Lawson told the crowd there she had felt “trapped” when a manager made unwanted advances.

“We have the strength to protect one another and demand the justice we deserve,” she said.

Restaurant workers account for a huge slice of the United States labor force, with the fast food sector creating more jobs than nearly any other in the past decade. But restaurants typically pay low wages and employ a disproportionate number of young people and women, making those who work in the industry particularly vulnerable to sexual harassment.