It was first proposed four days after King's 1968 assassination outside a Memphis motel. It took 15 years until it became a federal holiday.

Every year we honor the legacy of Martin Luther King Jr. in January. Here's everything you need to know about the holiday.

Though the holiday is young, this will only be the 25th year that all 50 states recognize it together. Here's what's open and closed on Martin Luther King Jr. Day.