Martin Luther King Day is a federal holiday held on the third Monday of January. It celebrates the life and achievements of Martin Luther King Jr., an influential American civil rights leader. He is most well-known for his campaigns to end racial segregation on public transport and for racial equality in the United States.
In 1968, shortly after Martin Luther King died, a campaign began for his birthday to become a holiday to honor him. Trade unions lead the campaign for the federal holiday after the first bill was introduced. It was endorsed in 1976. Following support from the musician Stevie Wonder with his single “Happy Birthday” and a petition with six million signatures, the bill became law in 1983. Martin Luther King Day was first observed in 1986, although it was not observed in all states until the year 2000. From timeanddate.com