On October 28, 1909, Clara Lemlich rose at a meeting at Cooper Union in New York City and delivered a speech in Yiddish calling for a general strike of the shirtwaist workers. The meeting had been going on for hours; speakers had been discussing the possibility of a strike without committing to it. Lemlich, a twenty-three-year-old immigrant who had been beaten by company thugs during an earlier labor action, interrupted the main speaker and demanded an immediate vote. The audience voted unanimously.

The Uprising of the 20,000 — the largest strike by women workers in American history to that point — began the next day. The women workers in the shirtwaist factories of New York were primarily Jewish and Italian immigrants, working ten to twelve hours a day in unsafe conditions, earning wages that left them in poverty. The strike lasted three months. It produced union contracts covering the majority of the shirtwaist industry.

Lemlich was born in 1886 in Gorodok, Ukraine, and emigrated to the United States in 1903. She joined the International Ladies' Garment Workers' Union, organized workers in her factory, and participated in earlier strikes that earned her multiple beatings and arrests. She was blacklisted from the garment industry after the 1909 strike.

She continued organizing for the rest of her life: suffrage campaigns, consumer boycotts, anti-fascist organizing in the 1930s, tenants' rights organizing in Los Angeles after World War II. She died in 1982 in a nursing home in Los Angeles, still organizing — she led a union drive among the nursing home workers at ninety-six.