King was in Memphis to support a strike by the city's sanitation workers when he was murdered in 1968. Although his strident support for workers' rights surfaced some year after his civil rights victories, many believe King saw both as one in the same.
Ben Jealous, president of the NAACP, says with public employee unions under a growing threat in states such as Maine and Wisconsin, it's time to recall King's dream.
"This work to bring together working people, struggling people, aspiring people -- who make up the great 98 percent of citizens in this county, to defend the rights of migrants in this country to defend the rights of unions in this country is very much what Dr. King was about," he says.
Hundreds of protestors filled the block at 15th and Pennsylavia in Northwest D.C.