Washington (CNN) -- A day before the United States observes Martin Luther King Jr. Day, park rangers placed wreaths at the Washington memorial honoring the civil rights leader.
Members of King's family stood beside the towering 30-foot statue of him as crowds sang "Happy Birthday" at a ceremony Sunday.
"We're celebrating the best of what we are, but also what we must become, knowing that we've not arrived there yet," Martin Luther King III said.
The civil rights leader's son said his father would have turned 83 Sunday, if he had survived the 1968 shooting that killed him.
On his last birthday, in January 1968, Martin Luther King Jr. was planning a "poor people's campaign" to bring together Americans from all walks of life to demand "decent jobs with decent pay," his son said.
"He did not live to see that come to fruition, and so, 44 years later, we're still challenging our nation, particularly in light of the fact that there's so much poverty rampant in this nation," Martin Luther King III said.
Among the many visitors at the memorial was Bill Janocha, from Stamford, Connecticut, who had traveled to Washington with a Boy Scout troop.
"He brought beautiful things to our country," he said about the elder King. "He ... was a monument ... so all the tributes that we can give him are certainly just."
The Martin Luther King Jr. memorial in Washington opened to the public last year. Sunday's ceremony came several days after officials confirmed that a controversial quote on one side of the monument would be corrected.
The line currently reads: "I was a drum major for justice, peace and righteousness."
The quote, which holds a prominent place among more than a dozen King's most notable lines at the site, sparked controversy last summer when poet Maya Angelou said it made the civil rights leader appear arrogant.
King's original words, from a 1968 sermon at Ebenezer Baptist Church in Atlanta, were: "If you want to say that I was a drum major, say that I was a drum major for justice. Say that I was a drum major for peace. I was a drum major for righteousness. And all of the other shallow things will not matter."
Angelou said that leaving out the "if" changes the meaning.
Interior Secretary Ken Salazar has given the National Park Service 30 days to consult with the Martin Luther King Jr. National Memorial Project Foundation, members of the King family and others to decide on a more accurate version of the quote, an official at the Interior Department said last week.
King's son said Sunday that he supported the move, because future generations may not know the context of the quote.
"The context is what I think people have questioned, and understanding and knowing who my father was, it could be confusing. For us today, no, but for generations yet unborn, they may not understand," he said. "But I'm sure that when this is done, that everyone who comes will understand who and what Martin Luther King Jr. meant in terms of what he said about himself."