Our live coverage has ended. Read below to see how the day unfolded.
Bells across the nation rang 39 times tonight about the time that Martin Luther King Jr. was gunned down 50 years ago in Memphis, Tennessee.
Bells rang for each year the civil rights leader lived.
In Atlanta, King's youngest child, Bernice King, rang a bell at his gravesite.
Members of his family also laid a wreath at the crypts of King and his widow, Coretta Scott King.
Sen. Bernie Sanders joined marchers today in Memphis, Tennessee, to pay tribute to Martin Luther King Jr.
"He was a nonviolent revolutionary," the Vermont lawmaker told a crowd at a rally. "He was a man who wanted to transform our country morally, economically and racially."
Sanders said Americans must follow King's legacy to transform the country.
"We have common dreams. And today, we tell the President of the United States and anybody else, you are not going to divide us up," she said.
Marc Morial, president and CEO of the National Urban League, said today should be remembered as the anniversary of Martin Luther King Jr.'s demands for African-Americans families.
"If we want a living wage, Martin Luther King would say, 'We must agitate. We must organize. We must legislate, but we must vote,'" he said, speaking to a crowd at the National Civil Rights Museum in Memphis.
Americans must vote to ensure King's legacy lives on, said Morial, whose organization focuses on economic development in urban areas.
"In 2018, to ensure that the dream, to ensure that the vision, to ensure the commitments of Martin Luther King remain real, we must agitate. We must organize and we must vote," he said. "And we must stay woke."
J. Lawrence Turner, a pastor at Mississippi Boulevard Christian Church in Memphis, urged fellow faith leaders to "pick up the mantle" and take actions against injustice.
He also called on faith leaders to follow Martin Luther King's teachings.
"I can hear Dr. King calling to us and saying to us that, 'We cannot wait,'" Turner told a crowd gathered today at the the National Civil Rights Museum in Memphis.
Crowds gathered today at the museum, where King was slain while standing on the balcony of the Lorraine Motel.
The daylong tribute there -- featuring speeches, videos, and singing and spoken-word performances -- is largely being held in the courtyard of the motel, now home to the museum.
Yolanda Renee King, the eldest granddaughter of the Martin Luther King Jr., said Wednesday that the civil rights icon would recognize "we're not where we're supposed to be" were he alive today.
"I think that he would be impressed about all the work that we're doing but we're not where we're supposed to be," the 9-year-old told ABC's "Good Morning America" on the 50th anniversary of MLK's assassination.
Last month, Yolanda made a surprise appearance at the March for Our Lives in Washington, D.C., which demanded measures to address gun violence.
Watch her speech:
Civil rights icon Rep. John Lewis, a Georgia Democrat, reflected today on the life of Martin Luther King Jr.
Lewis took to twitter to describe the day he found out that King was assassinated.
"50 years ago today, I learned the painful news that my friend, my mentor, Dr. Martin Luther King, Jr. had been assassinated in Memphis, TN," he tweeted. "He was my brother, my leader--that day it felt like something died in all of us."
Lewis' skull was fractured in 1965 during an attempted voting rights march from Selma, Alabama, to Montgomery, Alabama. He later joined King at the March on Washington.
As a college student in Memphis, Tennessee, Clara Ester was following the sanitation workers' strike that had brought the Rev. Martin Luther King Jr. to town in April 1968. She was with some of his associates outside the Lorraine Motel, walking to a diner to have some catfish, when she heard the gunshot that ended his life.
Ester told CNN's Erica Hill that every April 4 since then has been difficult to bear, in part because pictures from the assassination scene are re-circulated in the news media.
But it's more difficult to deal with now, she said.
Here's what she told CNN about how her father would view these modern movements:
"First of all, I think he would be excited. My father never lost hope. Even when it became dark and dismal and looked like his dream became a nightmare. He said he still maintained hope and so that hope is because he knew that there would always be a what he called a dedicated minority who would be committed to justice and peace and equity and to see young people rising up the way that they've been rising up, starting with the Black Lives Matter and coming forward to #MeToo, the women's movement and the young people that have been raising their voices recently with March for Our Lives. He would say that there's a resurgence."
She continued: "I'm sure that he would be making connections with these movements to make sure that they had what they needed in terms of understanding organizational strategy and planning so that they could bring about effective change."