Photos: Snapshots of Martin Luther King Day Across the United States

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Black rights protesters gather near illuminated letters spelling "DREAM" outside a house which they identified as the residence of Oakland Mayor Libby Schaaf, in Oakland, California January 19, 2015. The group, of about 30, projected images of Martin Luther King, Jr. onto the home's garage,as they called on the mayor to fire police officers with violent records. Noah Berger/Reuters

People across the United States, from schoolchildren to the President, marked Martin Luther King Jr. Day Monday by participating as volunteers, demonstrators, protesters and organizers.

Some marched to commemorate the iconic civil rights movement leader who would have turned 86 this year, while others gathered to protest police brutality and the loss of lives in incidents that brought long-simmering racial tensions to the surface over the last few months.

Some individuals and groups devoted Monday to volunteer as part of a "Day of Service" in honor of King, while others took the opportunity to celebrate his achievements through cultural and educational events.

Here are snapshots of the myriad ways the U.S. marked MLK Day:

Across the country, people participated in protests against excessive use of police force they feel is targeted disproportionately towards minorities. Demonstraters used slogans such as "Black Lives Matter," which emerged after the August fatal shooting by a policeman of unarmed teenager Michael Brown in Ferguson Mo., and "I Can't Breathe," the words uttered by Eric Garner, who died after being placed in a chokehold by a policeman in Staten Island in July. In Cleveland, protesters gathered at the site where 12-year-old Tamir Rice was fatally shot by Ohio police in November.

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People attend a Martin Luther King day rally in the Harlem section of New York January 19, 2015. Tributes to civil rights leader Martin Luther King Jr. were held around the United States on Monday as protests over the treatment of minorities by law enforcement rolled on across the country. Observers of Martin Luther King Jr. Day have this year linked the federal holiday to a rallying cry in recent months during demonstrations over police brutality: "Black lives matter." Carlo Allegri/Reuters
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T-shirts with the image of Martin Luther King and with the words "I can't breathe" are pictured for sale during a Martin Luther King day rally in the Harlem section of New York January 19, 2015. Carlo Allegri/Reuters
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Civil rights activist Reverend Al Sharpton speaks during a Martin Luther King day rally at his National Action Network in the Harlem section of New York January 19, 2015. Carlo Allegri/Reuters

President Barack Obama called for Americans to volunteer in tribute to Martin Luther King Jr. in a video posted on YouTube Monday. "Today, we come together in a National Day of Service, because as Dr. King once said, 'Life's most persistent and urgent question is: What are you doing for others?'" he said. Obama, along with the First Lady Michelle Obama and their daughter Malia, visited a Boys & Girls club to help paint murals and put together literacy kits. Elsewhere, people marked the day with other volunteer events, performances and services.

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U.S. President Barack Obama works on a literacy project with children during a day of service at the Boys & Girls Club of Greater Washington, in celebration of the Martin Luther King, Jr. holiday in Washington January 19, 2015. Jonathan Ernst/Reuters
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Randall Toussaint and his son Ethan visit the crypt of Dr. Martin Luther King Jr. and his wife Coretta Scott King prior to The King Center's 47th Annual Martin Luther King Jr. Commemorative Service in Atlanta January 19, 2015. Christopher Aluka Berry/Reuters
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People sing "We Shall Overcome" at the conclusion of The King Center's 47th Annual Martin Luther King Jr. Commemorative Service in Atlanta January 19, 2015. Christopher Aluka Berry/Reuters
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Actor and activist David Oyelowo, who portrays Martin Luther King Jr. in the movie "Selma", takes a moment while addressing the audience during The King Center's 47th Annual Martin Luther King Jr. Commemorative Service in Atlanta January 19, 2015. Christopher Aluka Berry/Reuters
Photos: Snapshots of Martin Luther King Day Across the United States | U.S.