In this Aug. 28, 1963, file photo, Dr. Martin Luther King Jr., head of the Southern Christian Leadership Conference, addresses marchers during his "I Have a Dream" speech at the Lincoln Memorial in Washington.

AP

In this Aug. 28, 1963, file photo, Dr. Martin Luther King Jr., head of the Southern Christian Leadership Conference, addresses marchers during his "I Have a Dream" speech at the Lincoln Memorial in Washington.