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.

Jan. 20 marks Martin Luther King Day, a federal holiday, which just so happens to coincide with Inauguration Day this year, both listed as federal holidays.

Here’s what to know about Martin Luther King Jr., why we celebrate his impact each year and when MLK Day is in 2025.