How Martin Luther King Jr. Day became a federal holiday

• A bill proposing a federal holiday honoring Martin Luther King Jr. was first introduced in 1968.
• It became a federal holiday in 1983 when then-President Ronald Reagan first signed a bill into law.

Martin Luther King Jr. is the most decorated civil rights icon in American history. But it took more than a decade after he died for the country to celebrate him with a national holiday.

Martin Luther King Jr. Day is the second federal holiday of every calendar year (after New Year's Day). The holiday marks King's birthday, which was on January 15, 1929.

Although MLK Jr. Day falls on King's actual birthday this year, that's not always the case.

Instead, the King Holiday Bill, which sought to make his birthday a legal public holiday, designated the third Monday of every January as MLK Jr. Day.

The bill was first introduced on April 8, 1968, four days after King was assassinated in Memphis, Tennessee, according to the National Museum of African American History & Culture. King was assassinated on April 4 of that year at the Lorraine Motel in Memphis.

The King Holiday Bill was a bipartisan measure sponsored by Democratic Rep. John Conyers of Michigan — a founding member of the Congressional Black Caucus — and Republican Sen. Edward Brooke of Massachusetts.

The House of Representatives first voted on the King Holiday Bill in 1979, 11 years after it was introduced. It didn't pass until four years later.

The bill's passage was a hard-won fight and didn't just involve lawmakers.

Music legend Stevie Wonder dedicated the song "Happy Birthday" to King in 1981, singing, "There ought to be a time that we can set aside to show just how much we love you."

Two years later, President Ronald Reagan signed the measure into law — in 1983, 15 years after it was first introduced — and it took nearly two more decades for all 50 states to observe the day, according to the National Museum of African American History & Culture.

The first time Martin Luther King Jr. Day was officially observed was in 1986, according to Time.

But only 27 states and Washington, DC, observed it at the time. It took another 14 years for all the states to observe it, per Time.

South Carolina became the last state, in 2000, to officially designate Martin Luther King Jr. Day as a federal holiday. It was the same year the state took down the Confederate flag from its statehouse.

In some states, King shares the day. Alabama and Mississippi also designate the third Monday in January to honor the Confederate general Robert E. Lee.

As part of Martin Luther King Jr. Day, public schools and universities are closed, and it's a bank holiday. The USPS is also closed, and public libraries are generally closed. National parks will be open on the day and are offering free admission.

King, former President George Washington, and Christopher Columbus are the only public figures with federal holidays recognizing them.

"To me, [King] is the outstanding international leader of the 20th century without ever holding office," Conyers said in 2015. "What he did — I doubt anyone else could have done."