In her speech, the actress said on Friday that sexual assault and harassment is not isolated to Hollywood.
"What has happened to me behind the scenes has happened to others in society and I cannot stand. I will not stand," said the actress.
While addressing the people, McGowan said, "I have been silenced for 20 years. I've been slut shamed.. harassed,.. maligned. And you know what, I'm just like you."
The event was attended by thousands of people who gathered there for workshops, keynote speeches and music.
The event is an offshoot of the Women's March protests that swept America in January, reports CNN.
This was McGowan's first public appearance ever since charges of sexual harassment against Hollywood mogul Harvey Weinstein came to light.
Earlier, she took to her Twitter handle to accuse the Hollywood mogul of raping her.
"I came to be a voice for all of us who've been told we are nothing. For all of us who have been looked down on. For all of us who have been grabbed by the motherf***ing p***y," added the actress.
McGowan is one of those women who have accused Weinstein of sexual assault and harassment. (ANI)