This week, America marks Martin Luther King Jr. Day: a national holiday celebrating the life and legacy of the great civil rights leader. As our way of honoring Dr. King, we're telling the story of "Happy Birthday." That would be the version that's often called "the black happy birthday song," the version written and originally performed by Stevie Wonder. It's a tribute to MLK, and it will always be associated with the 15-year effort to designate this national holiday.

As a young boy, Stevie Wonder first heard about MLK during the Montgomery Bus Boycott. At age 15 he was thrilled to meet Dr. King and shake his hand, and like so many Americans Wonder was devastated to hear of the inspiring leader's assassination in 1968.

Wonder attended King's funeral, and soon joined Rep. John Conyers in support of a bill that would declare a national holiday in King's honor. The idea quickly gained momentum, but it would take years of tireless effort to pass the law, due to opposition by people like Sen. Jesse Helms, who painted King as a lawless communist.

While labor unions turned up the political heat, Wonder revisited a song called "Happy Birthday." He wrote the song after he set out to record the traditional birthday song for King, then realized he didn't know the music to that version. Being Stevie Wonder, he decided to just whip up his own birthday song, with lyrics paying tribute to MLK.

With the election of Jimmy Carter in 1976, America had a president who owed a debt to labor unions, and he endorsed the bill to name Martin Luther King Jr. Day. Even that wasn't enough. Sensing that the tide was turning, Wonder recorded his version of "Happy Birthday" to include on his 1981 album Hotter Than July.

Wonder also rallied for the holiday, appearing alongside King's widow Coretta Scott King. He planned a four-month tour to publicize the drive for MLK Day, with a rally on the National Mall to cap the tour. Bob Marley was originally scheduled to be Wonder's tourmate, but the illness that would ultimately kill the reggae star made that an impossibility. Instead, poet and songwriter Gil Scott-Heron filled in. The tour was full of powerful moments, including one of unexpected poignancy when John Lennon was killed and Wonder had to make an announcement from the stage.

The movement to name MLK Day finally succeeded in 1983, but not without a final burst of drama as Helms actually mounted a filibuster to block the bill. President Ronald Reagan had long been on record opposing the new national holiday, but public pressure had mounted to the point that he reversed himself and signed the bill after it passed the Senate, 78 to 22. "It's a tyranny of the majority!" cried Helms.

When the holiday was first officially celebrated on Jan. 20, 1986, the occasion was marked by a concert featuring Wonder as the headlining artist. The show climaxed with Wonder leading a giant "Happy Birthday" singalong while a jubilant crowd waved glow sticks. A televised special showed Wonder singing along with dancing, clapping celebrities like Diana Ross, Harry Belafonte, Lionel Richie, Emmanuel Lewis, Neil Diamond, Eddie Murphy, and — wait, standing next to Elizabeth Taylor, is that Bob Dylan in a blazer with rolled-up sleeves?

At the time, a 24-year-old Barack Obama was working as a community organizer in Chicago. Three decades later, Obama would present Stevie Wonder with the Presidential Medal of Freedom.

Stevie Wonder has continued to sing his version of "Happy Birthday," which has been embraced as a civil rights anthem and a celebration of hope, particularly among African-Americans. With all due respect to Patty and Mildred Hill (and the Beatles), if you want to bring down the house with a happy-birthday song, it's hard to beat Stevie's.

We want to thank Marcus Baram, whose 2015 history of the song helped us connect a lot of dots for this episode.