Commemorations are taking place across the US to honour the legacy of black civil rights leader Martin Luther King, who was assassinated 50 years ago.
At the Memphis motel where Dr King was shot, a day of performances and speeches were set to take place.
A private sermon was held on Tuesday at the church where Dr King delivered his “I’ve been to the mountaintop” speech the night before he was killed.
Dr King, whose birthday is marked by a federal holiday, is held as a US hero.
But during his lifetime he was seen as a controversial figure and considered by the US government to be a dangerous agitator.
Dr King, known to many Americans as MLK, was gunned down by a sniper while standing on his balcony during a trip to Tennessee to protest the low pay of sanitation workers.
More on MLK’s legacy
Hundreds of people were expected to convene in Washington, DC for a silent prayer walk on Wednesday from the MLK Memorial, which was erected in 2011, to the National Mall.
On Tuesday night at Memphis’ Mason Temple Church of God in Christ, where he a speech the night before he was killed, Dr King’s daughter the Reverend Bernice King spoke about the difficulty of publicly grieving her father.
“You are looking at two children who lost their father,” Rev King said, after her brother Martin Luther King III joined her in the pulpit.
“It’s important to see two of the children who lost their daddy 50 years ago to an assassin’s bullet,” said Rev King, now 55.
“But we kept going. Keep all of us in prayer as we continue the grieving process for a parent that we’ve had yet to bury.”
Echoing her father’s words, she told the invitation-only audience: “One day we’ll all be able to join with Martin King and say ‘Free at last, free at last, thank God almighty we are all free at last'”.
In a video message, former president Barack Obama said “as long as we’re still trying, Dr King’s soul is still rejoicing”.
Civil rights leaders the Reverend Jesse Jackson, the Reverend Al Sharpton, US congressman John Lewis as well as rapper Common were expected to attend the Memphis events commemorating the anniversary.
On Wednesday evening in Dr King’s hometown of Atlanta, a wreath will be laid at his crypt.
Bells will toll across the country 39 times to honour the number of years Dr King lived at 19:01 local time – marking the moment he was gunned down.