WASHINGTON — Half a century after the emotional apex of the civil rights movement, Martin Luther King Jr.'s “I Have a Dream” speech, tens of thousands of people retraced his footsteps on Saturday, and his successors in the movement spoke of the still-unmet promise of America, as he did, at the Lincoln Memorial.

The anniversary of the 1963 March on Washington was less a commemoration, speakers proclaimed, than an effort to inject fresh energy into issues of economics and justice that, despite undeniable progress in overcoming racial bias, still leave stubborn gaps between white and black Americans.

The speeches that carried over the Reflecting Pool, which 50 years ago jolted Congress to pass landmark laws, took hard aim at current racial profiling by law enforcement, economic inequality and efforts to restrict voting access.

Addressing generations too young to remember, the Rev. Al Sharpton, an organizer of Saturday’s event, warned young people against the hubris of believing one’s middle class success was achieved alone. “You got there because some unlettered grandmas who never saw the inside of a college campus put their bodies on the line in Alabama and Mississippi and sponsored you up here,” he said.