The March on Washington brought more than a quarter-million people to the nation’s capital on Aug. 28, 1963, for what many consider a key turning point in the civil-rights movement.

The historic rally was highlighted by the “I Have a Dream” speech delivered by the Rev. Martin Luther King Jr. on the steps of the Lincoln Memorial.

Few realized it at the time—King’s speech did not even make the front page of The Washington Post the next day—but the calls for equal justice that echoed across the National Mall 50 years ago would be at least partially realized a year later with enactment of the Civil Rights Act of 1964.

“The response to our call to commemorate the March on Washington and my father’s ‘I Have A Dream’ speech has been overwhelming,” said Bernice A. King, who was exactly five months old when her father gave his best-known speech. “We expect hundreds of thousands of people to join us in the nation’s capital for this historic event, and many more to take part worldwide in their communities.”

King, who now heads the family’s King Center in Atlanta, has been the driving force behind the commemoration events that kicked off in Washington on Wednesday with a worship service at the Mt. Airy Baptist Church just north of the Capitol.

The biggest event in terms of participants will be the “Realize the Dream March and Rally” to be held Saturday on the National Mall. Organized by Martin Luther King III, King’s oldest son, and the Rev. Al Sharpton, leader of the National Action Network based in Harlem.