Martin Luther King, Jr. was the chief spokesperson for nonviolent activism in the Civil Rights Movement, which protested racial discrimination in federal and state law.

The campaign for a federal holiday in King’s honor began soon after his assassination in 1968. President Ronald Reagan signed the holiday into law in 1983, and it was first observed three years later. At first, some states resisted observing the holiday as such, giving it alternative names or combining it with other holidays. It was officially observed in all 50 states for the first time in 2000.

—Wikipedia