So everything that mkoren said was true. However, did you know that before Rosa Parks did all of that, there was another woman who did the same exact thing? Her name is Claudette Colvin, but she isn't famous. Let's learn why:
Claudette Colvin did the same exact thing as Rosa Parks: she wouldn't give up her seat on the bus. In the South during the 1860s-1950s, there were a set of laws known as "Jim Crow", which made it illegal for people of color to do many things. One such law applied to the bus system: people of color were only allowed to sit in the back of the bus, but if the front of the bus filled up with white people, people of color had to give up their seats to stand. 15-year-old Claudette refused to give up her seat to a white person when the bus was full, and as a result she was taken to jail.
So why doesn't anyone know about her? During the Civil Rights Era, people of color, specifically African Americans, were campaigning for equal rights. Now campaigning is the important word here: to campaign is "to work in an organized and active way toward a particular goal, typically a political or social one" (Merriam Webster). When Civil Rights leaders were campaigning, they wanted to change the image of African Americans that many White Americans had. Although most White Americans had never gotten to know or even met an African American due to segregation, White Americans held many negative stereotypes about African Americans.
Unfortunately, Colvin fulfilled many of the stereotypes that White Americans held about African Americans. She had very dark skin, she had a fiery, independent spirit, and she was a single teenage mother. So, when Colvin took her case to NAACP (National Association for the Advancement of Colored People), they decided to use the idea of her situation but to present the case through a milder, sweeter woman: Rosa Parks. 9 months later, Rosa Parks refused to give up her seat, and the story we all know begins.
For more information, check out this article on NPR: http://www.npr.org/sections/codeswitch/2015/02/27/389563788/before-rosa-parks-a-teenager-defied-segregation-on-an-alabama-bus