Martin Luther King was assassinated in 1968. After his death, Democratic U.S. Congressman John Conyers of Detroit and Republican U.S. Senator Edward Brooke of Massachusetts introduced a bill to make King’s birthday a national holiday. Not everyone in congress agreed, however, and it wasn’t until 1983 that the holiday was signed into law by then-president Ronald Reagan. Still, some states resisted observing the holiday and it wasn’t until 2000 that it was officially observed for the first time in all 50 states. The day is now celebrated nationwide on the third Monday in January, which is near King’s January 15th birth date.