Mary Ellen Mark often gave a half-joking response when asked why she'd never become a war photographer: "You have to be a fast runner," she'd say, "and that's not part of my nature."
In fact, Mark, who is acknowledged as one of the greatest American documentary photographers, ran from very little. She chronicled homeless families in Los Angeles and runaway children in Seattle, checking in with them over the years and producing stark but empathetic portraits as they aged. For six weeks, she lived in a psychiatric ward with severely disturbed women in Oregon. Over 10 years, she tried in vain to photograph brothels in Mumbai, where prostitutes at last came to trust her so much that they hid her under a bed during a police raid.
Mark, 75, died Sunday in a New York City hospital. She had a blood illness associated with failing bone marrow, her friend Kelly Cutrone told the Associated Press.
Self-effacing and gregarious, Mark sold her work to magazines such as Life and Look when there was a greater appetite for storytelling in black and white from the ends of the Earth and the edges of society.
"She was just interested in people and understanding them on a personal level," said Lisa Hostetler, the curator in charge of photography at George Eastman House in Rochester, N.Y., which owns more than 125 prints by Mark.
"She was the ultimate humanist," Hostetler said. "You could see it in the connection she had with her subjects."
Commissioned by Life for a story on runaways in the early 1980s, Mark captured haunting images of Seattle street kids — here a small boy with a large gun, there a teen clutching a rag doll.
Mark developed a decades-long friendship with a girl named Tiny, first photographing her as a rebellious 13-year-old doing drugs and turning tricks. Years later, Mark photographed the birth of Tiny's first baby. In recent years, she focused on the middle-age Tiny's more settled life as a wife and mother of 10.
"Their relationship would appear to breach the line typically drawn between documentarians and their subjects," the Seattle Times wrote in 2003. "When Mark talks about Tiny and her 'beautiful' children, her voice carries all the affection of a doting aunt or grandmother."
Mark compiled a book about Tiny and the other runaways called "Streetwise." In 1984, she collaborated with her husband, filmmaker Martin Bell, on a "Streetwise" documentary that was nominated for an Academy Award.
Mark was born March 20, 1940, in Philadelphia, was a high school cheerleader, attended the University of Pennsylvania and, in 1964, received a master's degree from the university's Annenberg School of Communications.
She didn't become serious about photography until picking up a camera in graduate school — and then, no other profession would do.
"It's given me my life," she told the Ithaca Journal in 2008. "It's still giving me a fantastically interesting life from the people I'm surrounded by because of it."
Mark published 18 books of photographs, with subjects as diverse as twins, high school proms, and the women of Ward 81. She preferred shooting in black and white and she avoided digital enhancements.
"I'm kind of a purist that loves reality — and that's not the trend now," she told a 2013 gathering at the Smithsonian American Art Museum. "Now they want very commercial, very decorated illustrations."
Mark photographed circuses and suffering. She had "an uncanny ability to capture the uncanny," David Friend, Life's photo editor, told The Times in 1991.
In Kolkata, Mark worked at the hospices run by Mother Teresa, who, she said, made her sit under a stairwell "to learn humility."
Earlier, she spent six months shooting circuses in India and was bitten in the hand by an aggressive chimpanzee.
On a return visit the following year, the wary Mark was urged to shake hands with the caged chimp — who charged and apparently intended to take her arm off before she quickly withdrew it.
"Chimps are clever," Mark deadpanned to the Smithsonian group. "Their trainers are usually missing fingers."
She is survived by her husband. A previous marriage ended in divorce.