WILLIAMSTOWN, Mass. (AP) – Peggy Diggs wanted to create art that forces people to question the importance of money. What better way, she reasoned, than to use currency as her canvas.

Two years ago, the Williams College faculty member began stamping cash with thought-provoking questions like, “Do you feel the need to be paid for everything you do?” and “What is satisfied in you by buying things?”

Every bill that passes through Diggs’ wallet gets a stamp. With the help of 10 friends, relatives and fellow artists, she estimates she has circulated at least $100,000 in stamped money.

It’s fair to say millions of people have unwittingly laid hands on Diggs’ work, an audience few artists can match.

“It’s kind of like graffiti, but in a small, private way,” she said. “I just love that there are people out there I’ve never met who are thinking about ways money has hurt them.”

The money-stamping project is just one of her many works of “public art,” a genre-bending form that defies artistic conventions. It’s not the kind of art that hangs in museums and galleries. It’s not the kind that makes Diggs any money, either.

“Sometimes the work takes a form that doesn’t look like art at all,” she admits.

She has plastered buses in Boston with children’s artwork. She has decorated milk cartons in New Jersey with a message about domestic violence. Her next project involves working with prisoners in Pennsylvania on developing products for people living in cramped spaces.

Erin Donnelly, curator of the Lower Manhattan Cultural Council, said public artists like Diggs are stretching the traditional boundaries of art.

“Her work draws a solid connection between art and everyday life in a meaningful way,” said Donnelly, whose council awarded Diggs a five-month residency last summer.

Patricia Phillips, chairwoman of the art department at the State University of New York-New Paltz, said the money-stamping project is just as artistic as any painting or sculpture.

“I think it’s art because she is taking this very common and banal system of distribution and intervening, bringing another message into this currency,” said Phillips, who wrote an essay on Diggs’ work in a book called, “But Is It Art?”

Manhattan artist Gregory Sholette, Diggs’ friend and fellow public artist, says the definition of art is constantly changing.

“Everything under the sun has been brought into the art gallery at some point,” he said, “from dirt on a floor to toilet fixtures to paintings.”

Diggs’ art has taken her all over the country over the past 14 years. Traces of the work fill the studio in her Williamstown home.

In Boston, she collaborated with at-risk youths to decorate MBTA buses with billboards about the perils of street violence.

In a Hartford, Conn., neighborhood torn apart by gang warfare, she initiated a dialogue between elderly women who were afraid to leave their homes and teens who also felt threatened by gang members. Their words were printed in a newspaper insert.

In Chicago, she helped homeless women create large banners with slogans challenging stereotypes about homelessness. The banners blanketed the buildings and streets of a crack-infested neighborhood.

In 1992, she persuaded a New Jersey dairy to distribute 1.5 million milk cartons that asked, “When you argue at home, does it always get out of hand?” Underneath the shadow of a menacing hand was the number for a national domestic violence hot line.

That project, perhaps her best-known work, was inspired by her meetings in a Rhode Island prison with battered women who killed their abusers.

“I see my art as an excuse for dialogues with people I otherwise never would get a chance to meet,” Diggs explained.

Her latest project is an even bigger departure from the confines of conventional art forms. Diggs recruited a group of inmates at a maximum-security prison near Philadelphia to help her design “problem-solving” products for people who live in confined spaces.

“I’m a deep believer that everyone is an expert at something,” she said. “What they know can be useful both for the most extreme situations, like refugee camps, to the more common, like small apartment life.”

During her first visit to the Graterford, Pa., prison, in January, one of the inmates told her how to make a “microwave” out of aluminum foil, wire and a light bulb. Another said he could make a radio out of a battery and items from his cell.

“My goal isn’t to exploit these guys, but to put their expertise to work in a way that’s useful for other people,” she said.

Diggs, 58, didn’t train her eye on socially conscious art until the late 1970s, when she and her husband, Ed Epping, left Central Michigan University and took jobs at Williams, in the Berkshire Hills of northwestern Massachusetts.

“All of a sudden,” she recalls, “a flip switched. I needed to get out and do things, not just sit in the Ivory Tower. Coming to a place that was so quiet, it made me want to bust out.”

She also lost interest in the mainstream, “elitist” art scene, “where the chosen speak to the chosen, and the art star dominates the show.”

Public art, she added, “made me feel like more of an activist using my work rather than just making objects to consume.”

It doesn’t bother Diggs that most of her work, including the money-stamping project, is virtually anonymous.

“I specifically designed the stamps so my name isn’t on it,” she said. “That way, there’s no way people can get distracted from the message itself.”