Tributes to civil rights leader Martin Luther King Jr. were held across the United States on Monday as protests over the treatment of minorities by law enforcement rolled on across the country.

This year, observers of Martin Luther King Jr. Day have linked the federal holiday to a rallying cry in recent months during demonstrations over police brutality: "Black lives matter."

King's 1960s dream of racial equality was being viewed through a lens focused on the recent deaths of unarmed black men after confrontations with police, including Eric Garner, who died in July after being put in a chokehold in New York City, and Michael Brown, who was shot in Ferguson, Missouri, in August.