This year marks the 40th anniversary of US President Ronald Reagan signing into law the bill that established Martin Luther King Day.

For three years Wonder put his life on hold and dedicated tours, rallies and marches to bring his vision to life – a quest that would establish the first holiday in the US that honoured a black American. The 1980 song had represented the start of Wonder's campaign to make the birthday of renowned peace activist, Martin Luther King Jr, into a federal holiday. 'I just never understood/ How a man who died for good/ Could not have a day that would/ Be set aside for his recognition,' they sang, electrifying the crowd. The 50,000-strong audience chanted: 'Martin Luther King Day, we took a holiday,' according to Scott-Heron’s 2012 memoir, The Last Holiday, as the stars began to sing Wonder's hit song, Happy Birthday, a tribute to the murdered civil rights leader. On 15 January 1981, music legends Diana Ross and Gladys Knight, along with the 'godfather of rap', Gil Scott-Heron, joined renowned musician Stevie Wonder on stage at the National Mall in Washington, DC.

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