As they do each year on the third Monday in January, Americans are celebrating the legacy of Martin Luther King Jr., the iconic leader of the African-American civil rights movement who was assassinated in 1968.
Across the country, parades, neighborhood events and community service projects were being held to honor the Baptist minister who won the Nobel Peace prize in 1964 for advocating non-violent activism.
His widow, the late Coretta Scott King, once wrote that the holiday celebrates the life and legacy of a man who brought hope and healing to America. She noted the values he taught through his example of courage, truth, justice, compassion, dignity, humility and service.
Civil rights advocates march to honor the Rev. Martin Luther King Jr. in Washington, D.C., Jan. 14, 2017.
"On this holiday, we commemorate the universal, unconditional love, forgiveness and nonviolence that empowered his revolutionary spirit," she said.
Hundreds of thousands of people were expected to march Monday in parades and demonstrations in hundreds of U.S. cities and towns, emulating King's marches for justice in the 1950s and ‘60s.
The holiday is designated as a National Day of Service as hundreds of community centers and volunteers across the country donate their time to make a difference in their neighborhoods. They pick up litter and trash along streets and in parks and empty lots, help repair blighted homes, and feed the poor and homeless.
In his proclamation marking the holiday, outgoing President Barack Obama indirectly noted November's closely contested presidential election, saying, "We must live our values, strive for righteousness, and bring goodness to others. And at a time when our politics are so sharply polarized and people are losing faith in our institutions, we must meet his call to stand in another person's shoes and see through their eyes. We must work to understand the pain of others, and we must assume the best in each other."
President-elect Donald Trump met Monday with King's son, Martin Luther King III, to discuss voting rights. After the meeting, King told reporters the talks were very constructive and that Trump promised to represent Americans.
WATCH: King III on 'Constructive' Meeting with Trump
Earlier, Trump spokesman Sean Spicer said on NBC's Today show that Trump and King planned a conversation "about bringing more people into the system, the legacy of Dr. King, and how we can continue to pursue that under the Trump administration."
Trump tweeted Monday, "Celebrate Martin Luther King Day and all the many wonderful things that he stood for. Honor him for the great man that he was!"