Martin Luther King Jr. may now be a nationally revered Civil Rights icon whose legacy is celebrated every January, but the road to name a federal holiday in his honor was not an easy one.

King, who spent the last years of his life advocating for nonviolent action against racial inequality in the United States, sparked a national movement and earned himself the Nobel Peace Prize in 1964.

Despite his accolades, it wasn't until nearly 20 years after his assassination in 1968 that Martin Luther King Jr. Day became federally recognized in 1986. And it was even longer until all 50 states recognized the holiday by 2000.

Here's the story of the fraught struggle to make MLK Day a day celebrated across the nation, and everything else to know about the holiday.

When is Martin Luther King Jr. Day?

On the third Monday of every January, the federal government shuts down for the day to honor Martin Luther King Jr.

The Baptist minister first came to national prominence during the 1955 Montgomery bus boycott in Alabama. King would go on to become one of the most prominent figures in the Civil Rights movement, founding the Southern Christian Leadership Conference in 1957 and leading the 1963 March on Washington.

The holiday in his honor is timed to honor King's birthday, though it rarely falls on that actual day because of the Uniform Monday Holiday Act, which former President Lyndon B. Johnson signed into law in 1968.

Born in 1929, King's birthday is Jan. 15, which in fact happens to be the day that MLK Day will be celebrated this year.

What is the meaning of MLK Day?

King advocated for civil disobedience and nonviolent methods to push back against racism and segregation.

As such, MLK Day was designated as a national day of service in which all Americans are encouraged to volunteer to improve their communities, according to the Smithsonian National Museum of African American History & Culture.

Across the nation, cities and local communities will host ceremonies and volunteer events on Monday.

Nationally, the King Center in Atlanta, Georgia is hosting a variety of events through Monday to commemorate King and honor those who embody the principles for which he stood. The NAACP will also host its annual King Day at the Dome event, which Vice President Kamala Harris is scheduled to headline.

How did Martin Luther King Jr. Day become a federal holiday?

The campaign for a federal holiday in King's honor began four days after he was assassinated on April 4, 1968.

James Earl Ray confessed to shooting King and was sentenced to 99 years in prison. King's killing sent shock waves through America and is still regarded as a landmark event in U.S. history.

But despite the national fervor inspired by the death of the leader who was instrumental in the passage of the Civil Rights Act in 1964, legislation to honor him languished for years, according to the National Constitution Center.

Undeterred by the lack of political support, Rep. John Conyers (D-Mich.) reintroduced the legislation every year with the backing of the Congressional Black Caucus, which he helped found. It wasn't for 15 years until after King's death that civil rights activists finally succeeded in making Martin Luther King Jr. Day a nationally observed holiday.

On Nov. 2, 1983, President Ronald Reagan signed a bill making the third Monday in January a federal holiday in observance of King's legacy. The holiday was first observed three years later on Jan. 20, 1986.

How did Stevie Wonder help?

Years before Reagan signed the bill, the legislation had been struck down by the House in 1979 even as President Jimmy Carter called on Congress to pass it.

Following the bill's defeat, musician Stevie Wonder released his song "Happy Birthday," an ode to King's vision that galvanized public support for the holiday by recognizing his many achievements, according to the King Center.

Wonder didn't stop there: The Motown singer made regular appearances alongside King's widow, Coretta Scott King, at rallies. Wonder capped a four-month tour with a benefit concert on the National Mall, where 18 years earlier King delivered his famous “I have a Dream” speech.

When the bill again made it to the House floor in 1983, Coretta Scott King and Wonder delivered a petition with 6 million signatures in favor of the holiday to the speaker. The bill easily passed in the House with a vote of 338 to 90.

At the Senate level, Republican Sen. Jesse Helms attempts to accuse King of being a communist didn't derail its momentum, and it passed in the Senate before heading to Reagan's desk, according to the Smithsonian.

When did all 50 states recognize MLK Day?

By this time, 17 states had already enacted King holidays of their own, the Smithsonian said.

Other states, though, were resistant to the idea of honoring King by name. Instead, they observed holidays with alternative names. Arizona and New Hampshire, for example, celebrated “Civil Rights Day," while Wyoming celebrated “Wyoming Equality Day," according to the Smithsonian.

It wasn't until 2000 that MLK Day was officially observed in all 50 states for the first time.

Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at elagatta@gannett.com

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