Half a century has passed since Martin Luther King Jr. led the March on Washington for Jobs and Freedom, yet thousands of demonstrators on Saturday commemorated the day by protesting against civil rights infringements they say continue 50 years later.

The NAACP gave out signs condemning voter identifications laws they say could bar some minority voters from the polls. And many vowed to continue to fight for equal rights for Latinos, gays, the poor and the disabled.

“This is not a time for nostalgic commemoration,” Martin Luther King III, the eldest son of the assassinated civil rights leader, said in a speech that channeled his preacher father’s tone. “Nor is this the time for self-congratulatory celebration. The task is not done. The journey is not complete. We can and we must do more.”

Eric Holder, the country’s first black attorney general, said gays, Latinos, women, and the disabled had yet to fully realize King Jr.’s dream. But he said without 1963’s protesters, who braved fire hoses, police abuse and shameless racism, neither he nor President Barack Obama would be in office.

“They marched in spite of animosity, oppression and brutality because they believed in the greatness of what this nation could become and despaired of the founding promises not kept,” Holder said.

Other speakers mentioned high unemployment among blacks, which is about twice that of white Americans, according to the AP. And many balked at the acquittal of George Zimmerman, who shot to death Trayvon Martin, an unarmed black teenager who many believe Zimmerman racially profiled.

“What happened to Trayvon Martin must never happen again,” NAACP President and CEO Benjamin Todd Jealous said in a statement advocating for the creation of “Trayvon’s Law,” which would repeal stand-your-ground gun laws. “Trayvon’s Law will serve as the foundation for community advocates as they work to end laws and practices that contributed to his death and to create new policy that will prevent future tragedies.”