The injustices that existed in 1963 convinced Johnson and her family and friends to attend the march.
"We had to be there. We had to be a part of it," she said.
The fight for equality that the original march embodied remains a work in progress, McRae said, which makes Saturday's event so important.
"We need this, especially now," she said.
Both women wore buttons from the march in 1963.
Saturday's event is the first of two rallies to mark the anniversary.
President Barack Obama headlines another event Wednesday, the exact anniversary of the March on Washington, where MLK delivered the now-famous speech at the Lincoln Memorial.
The Wednesday event will include a longer march through Washington and speeches by Obama and former presidents Bill Clinton and Jimmy Carter.