WASHINGTON, DC - JANUARY 21: Linda Sarsour speaks onstage during the Women's March on Washington on January 21, 2017 in Washington, DC. (Photo by Theo Wargo/Getty Images)

Muslim activist Linda Sarsour is one of four organizers spearheading the upcoming Women’s March on Washington. But her prominence as a social justice advocate didn’t happen overnight.

In a recent episode of Vox’s series “The Secret Life of Muslims,” Sarsour recounts the event that kickstarted her activism and what she sees as one of her biggest civil rights victories so far.

Sarsour was 21 years old when Sept. 11 occurred. A native New Yorker, she watched in dismay as her loved ones tried to hide their Muslim identity for fear of retaliation.

“My whole perspective on what country I lived in just changed in a matter of minutes,” Sarsour says in the video.

That experience prompted her to go volunteer at the Arab American Association of New York, and she hasn’t looked back. More than fifteen years later, Sarsour is now the organization’s executive director.

Sarsour has been active in some of the biggest social justice movements of our day ― including fighting for racial equality, fair policing and religious freedom. One of her greatest victories involved getting New York City to incorporate two Muslim holidays into the public school calendar ― making it the largest school district in the country to officially recognize the Islamic holy days.

In November, Sarsour was one of three activists and women of color invited to be national co-chairs of the Women’s March on Washington, scheduled to take place on the day after president-elect Donald Trump is sworn into office. The event is expected to draw more than 700,000 people to DC and other “sister marches” around the world.

Sarsour’s involvement with the march has thrust her into the spotlight in recent months. But anyone familiar with her work on the ground knows that for Sarsour, activism isn’t just a one-off event. It’s a lifestyle.