An African-American woman tries to sit in a seat on public transportation implicitly reserved for whites only. She refuses to get up when ordered to move, and is forcibly evicted by the police.
Her case draws national attention, and eventually causes the Supreme Court to confront the issue of racial segregation.

If you’re thinking of Rosa Parks in Montgomery, Alabama, you’re about a hundred years too late.
I’m talking about Kate Brown, a resident of the District, who in 1868 refused to leave the car reserved for white ladies in a train bound for Washington.