Rosa Parks and the Montgomery Bus Boycott

For all its advances in science, technology and human rights, the USA, untill not very long back(till the middle of the previous century), was following the barbaric practice of discriminating humans based on the colour of their skin. Blacks and Whites were segregated virtually in every aspect of public life.
There was simmering discontent among virtually the entire black populace. But the white man occupied every high position and there was pretty much nothing that the negroes could do about it.
That is, until Rosa Parks happened.

The first day of December in 1955 proved to be a turning point in the history of black America. Parks refused to relinquish her seat on the bus to a white man. She disobeyed the bus driver's repeated requests. The law of the day was that a black should vacate his/her seat to a white person. This led to her arrest and subsequent trial.

What followed was one of the most famous civil disobedience movements that the world has witnessed and the Montgomery Bus Boycott. The organiser of this boycott was, of course, Martin Luther King, Jr.
Rosa Parks' actions earned her a very important position in the annals of America's history.

Take a look here for Martin Luther King's "I have a dream" speech.