(CNN) -- The nation paused Monday to remember the Rev. Martin Luther King Jr., the civil rights icon who would have turned 83 this year had a bullet not cut short his life.
President Barack Obama marked the holiday with a service project at the Browne Education Campus in Washington on Monday morning.
He told the group it was the third year that he, his wife Michelle and daughters Malia and Sasha have engaged in some sort of service on King's birthday. While Malia was present Monday, Sasha "couldn't make it today," the president said.
"We're going to be doing a whole bunch of stuff to make the (school) facilities even better than they already are," Obama said.
He said there is "no better way" to honor King's life than by doing something on behalf of others.
"There's nobody who can't serve, nobody who can't help somebody else," he said. "Whether you're 7, or 6, or whether you're 76, you can find the opportunity to make an enormous amount of difference in your community."
Later Monday, the first couple will attend the Let Freedom Ring Celebration at the Kennedy Center.
U.S. Attorney General Eric Holder is scheduled to speak at the King Day at the Dome rally in Columbia, South Carolina on Monday, according to organizers of the event. The event will "commemorate Dr. King's life, draw attention to economic and educational equalities in the state, and protest the Confederate battle flag flying in front of the (state capitol) building," organizers said.
A federal holiday to honor King, who was assassinated in April 1968, was first observed in 1986. In 1994, Congress also designated it a national day of service.
On Monday, a group including Washington Mayor Vincent Gray, civil rights activist Dick Gregory and the Rev. Al Sharpton placed a wreath at the memorial honoring King.
"We must be reminded as to why Dr. King has been the one to deserve such a monument and such a holiday," Sharpton said. "... What he did was hold a banner of freedom and equality that actually transformed this nation."
On Sunday, park rangers also placed wreaths at the memorial. Members of King's family stood beside the towering 30-foot statue of him as crowds sang "Happy Birthday" at a ceremony.
"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.
On the civil rights leader's birthday -- January 15, 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.
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.
"It could be confusing. For us today, no, but for generations yet unborn, they may not understand," he said.
Athena Jones and Laurie Ure contributed to this report