At the White House Rose Garden on November 2, 1983, President Ronald Reagan signed a bill creating a federal holiday to honor King. Observed for the first time on January 20, 1986, it is called Martin Luther King, Jr. Day.
This was followed by President George H. W. Bush's 1992 proclamation, that this holiday was to be observed on the third Monday of January each year, near the time of King's birthday.
On January 17, 2000, for the first time, Martin Luther King Jr. Day was officially observed in all fifty U.S. states.
Reference: http://en.wikipedia.org/wiki/Martin_Luther_King,_Jr.