The abolition of slavery in the US was followed by years of racial segregation, especially severe in the Southern States. African Americans were prevented from voting, forbidden to share public space with white Americans and faced racial discriminations in all aspects of their lives, including access to the justice system where cases of violence and police brutality were never addressed. Little by little a non-violent Civil Rights movement was born. Following a successful bus boycott campaign, Reverend Martin Luther King Jr took the lead of the Civil Rights movement
On 28 August 1963, King spoke at the end of a protest in Washington DC for jobs and freedom. 250 000 people were gathered in front the Lincoln memorial where King delivered one of the most famous speeches in modern American history, known as the “I have a dream speech » . In his speech, King called for justice and democracy in the respect of the American Constitution and the declaration of independence, stating that the US forefathers « … were signing a promissory note to which every American was to fall heir. This note was a promise that all men, yes, black men as well as white men, would be guaranteed the unalienable rights of life, liberty, and the pursuit of happiness”.
This speech marked a corner stone for the Civil Rights movement in the USA, by putting greater emphasis on the movement nationwide but also in the rest of the world. This culminated with the adoption of the Civil Rights Act in 1964 and the ratification of the 24th Amendment of the Constitution, which lifted voting barriers. Martin Luther King also received the Nobel Peace Prize for his activism on December 10, 1964.
The speech marked people spirits because of its timeless call to respect the values of democracy; justice and non-violence. It also made the fulfilment of Civil Rights a matter of justice and freedom for all. By using this universal concept in the context of the American dream and values, King made a compelling case that resonated throughout the world.
Additional links and references:
 King Institute Stanford https://kinginstitute.stanford.edu/king-papers/documents