Farber: One of the great historical facts about the march was the difficulty in pulling off an event that was pioneered by a number of organizations and individuals with different definitions and investments of social change at the march.

(I see) the rich diversity of the "we": Although there are different groups and investments, you get a sense from photographs like these that it's not an "us" and a "them" but a "we".

It's not to erase the differences, or simply streamline them, but in co-existing, you get a richer vision of what social change can be.

CNN: How was this photography critical in the message of the march?

Farber: Leonard captured some important private reflective movements.

It's a lesson for us in thinking about great moments in history: what it takes to envision progress or possibility is both about moving forward and also about considering and questioning and stopping -- and having the patience for social change.

Part of what photography gives us is ... a sense of the high points of these great moments in history, as well as the unexpected glances that really capture the subjects (as) they have their own thoughts and own ideas, (and) relate to the broader group's perception throughout the day.