Rosa Parks.

On a cold December evening in 1955, Rosa Parks quietly incited a revolution, by just sitting down.
She was tired after spending the day at work as a department store seamstress. She stepped onto the bus for the ride home and sat in the fifth row (the first row of the "COLORED SECTION").
In Montgomery, Alabama, when a bus became full, the seats nearer the front were given to white passengers.
Montgomery bus driver James Blake ordered Parks and three other African Americans seated nearby to move ("Move y'all, I want those two seats,") to the back of the bus.
Three riders complied; Parks did not.
After Parks refused to move, she was arrested and fined $10. The chain of events triggered by her arrest changed the United States.