So there are actually quite a few parts to this. Although efforts to establish a holiday honoring the life of the civil rights leader began just days after his assasination in 1968, the federal holiday (the third Monday in January) wasn’t signed into law until 1983, and it was first observed in 1986.However, the story at the state level is a lot more complicated. Some states started observing the holiday (then on his birthday, Jan. 15) as early as 1970, but it wasn’t observed by every state until 2000, a full 14 years after the first federal observance. And even though all states now commemorate some version of Martin Luther King, Jr. Day, in a few holdouts it’s still combined with Robert E. Lee’s birthday.