The photographer Mary Ellen Mark was not interested in glamour. She wanted to document the lives of the “unfamous,” the troubled people who lived on the fringes of society. Born in 1940, in Pennsylvania, Mark began taking photographs as a child, using a Brownie box camera. During the Vietnam War she turned her lens to the women’s liberation movement and grew interested in transvestite culture. Over the course of her career, she focused on the tragedies of America’s despised populations—drug addicts, prostitutes, the homeless. “I feel an affinity for people who haven’t had the best breaks in society,” she once said. “What I want to do more than anything is acknowledge their existence.” Mark died in 2015. This is her first retrospective in a major museum. —Elena Clavarino