Jan. 20 is Martin Luther King Jr. Day in the United States. Here's what's open and closed during the national holiday.

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.

The holiday is the only federally-designated day of service. People are encouraged to participate in a “day of action” and spend the day doing something charitable to uplift their communities.