When Martha Cooper quit her job as a New York Post staff photographer to photograph graffiti full time, she did what all true believers must do: she sacrificed financial stability, status, and recognition from the establishment. All to pursue a passion rooted in the love and understanding for that which is universal and transcendent. When her first book, Subway Art (Henry Holt, 1984), co-authored with Henry Chalfant tanked upon release, Cooper was disappointed to discover her gamble did not pay off.

“I was shooting up until Subway Art got published, and I imagined it was going to be — maybe not a bestseller, but I did think there would be more of a reaction, but there was virtually no reaction,” Cooper says. “The trains kind of died off right then. They had cracked down right at that moment. Maybe it had to do with the book? I didn’t think so then.”

Unbeknownst to Cooper, the book took on a life of its own as it found its way into the hands of graffiti writers in every corner of the globe. It had become the “Graffiti Bible,” inspiring generations of artists to pick up a can of spray paint and leave their mark on society. Over the years, countless artists have studied the book with reverence, Cooper’s photographs providing not only a template of style but also a wealth of knowledge about the underground culture that birthed it.

While graffiti spread like a virus, Cooper went about her work documenting the vernacular arts of homespun communities with organizations like City Lore. It wasn’t until 2004 when she was on tour in Europe promoting her book Hip-Hop Files: Photographs 1979-1984 (From Here to Fame) that she discovered the impact of Subway Art, and reconnected with many of the writers she had photographed back in the days.

Suddenly everything had come full circle, and Cooper was back in the mix — just as street art was taking the world by storm. Over the past 15 years, Cooper has been flown around the globe to document graffiti and street art festivals and events, but in her heart, she maintained a love for illegal actions.

“It is so thrilling and so scary. Can I keep up? Can I get the picture?” Cooper asks. “It happens so fast. I am worried about my equipment and getting the right settings. It’s not like they are going to do it over again.”

Now in her 70s, Cooper still has it. Martha: A Picture Story, the documentary film directed by Selina Miles that premiered earlier this year at the Tribeca Film Festival, opens with a scene of Cooper running through a Germany train station alongside the notorious 1UP Crew as they spray massive smiley faces on the walls with paint-filled fire extinguishers.

It’s an exhilarating moment that gives us a taste of what it must have been like for the photographer to sneak inside New York City’s train yards and lay-ups in the dead of night alongside legends like DONDI. But, as the film makes clear, Cooper’s archive extends far beyond the graffiti-covered trains of the 1980s and continues up to her recent work documenting the streets of southwest Baltimore.

Cooper got her start as the first woman to photo intern at National Geographic in 1963 after completing a stint with Peace Corps and traveling from Thailand to England on a solo motorcycle trip. She moved to New York City during the 1970s, making “weather photos” for The New York Post, which were later published in the book New York State of Mind (powerHouse Books).

At that time the Post was headquartered on the Lower East Side, and Cooper hung out in the neighborhood photographing the kids who made the streets their playground. It was here that she first learned about graffiti and immediately set forth on a quest that would transform not only her life but the landscape of art.

“One of the things that got me into the graffiti was that these kids were doing it for each other," she says. "It was a pure form of art. They weren’t thinking about selling or making money. They had their own aesthetics and only they understood what those aesthetics were. I wanted to figure out what it was.”

“It was not meant for the public at large because they didn’t understand it. Adults hated the inside of the train because it represented New York out of control. As soon as I understood the tags were kids writing their nicknames and that you could identify them they became like a puzzle. There’s a ZEPHYR. There’s a REVOLT. Adults didn’t get it but I felt like I was on to something — I was!”