Charlotte Frank remembers heading downtown that brilliant September morning seven years ago toward her 63rd-floor office in Lower Manhattan, where she was an executive with the Port Authority of New York and New Jersey.

She never made it. Her office was in the North Tower of the Port Authority’s World Trade Center, and it was Sept. 11, 2001. She couldn’t get past Canal Street. She stood with dozens of onlookers and watched the first tower collapse. They uttered almost in unison, “Oh…my…God.”

Frank retired the next year at 67, after helping the agency get back on its feet. “I was on my way out,” she says. “But that precipitated it. You don’t know what’s going to happen to you, so you better get on with what you really want to do, your next act.”

She got on with it. Within days, she was working full time with no pay for the Transition Network, a New York nonprofit for women over 50 who are at or approaching retirement. Frank had founded the group two years earlier with her friend Christine Millen, then 58 and a partner at the consulting firm Deloitte & Touche.

Frank and Millen had spent many lunches trying to sort out what to do with their own retirements. They came to realize that they were on the leading edge of a generation of women better educated and more ambitious than any before. These were the first women to have reached top-level positions in business, government, and other fields, and they were facing possibly 30 years of retirement—without a road map. “We asked ourselves: ‘What do you do when you don’t have a purpose? What do you do when you don’t have your career? What do you do when you don’t have your identity? Your social network?’ It’s a time of major loss,” Frank says.

Bridge to change. Frank and Millen launched the fledgling outfit with no budget, staff, or office space but with a firm belief that they were on to something big, a grass-roots movement that “reimagines retirement.” The women broadly define retirement as a series of transitions—a bridge from one career to another or from employment to volunteerism, advocacy, or community. The challenge was to build networking peer groups to provide support and share information. “I wanted to continue to have an impact on the world and needed an organizational structure to do so,” Frank says. “You change the world by taking on large issues and large groups of people.”

For her first act, Frank chose a career in government, moving up the ranks in local, state, and federal programs dealing with civil rights, child welfare, and community development. Frank was chief operating officer for the U.S. Equal Employment Opportunity Commission under Eleanor Holmes Norton, supervising 3,000 field workers. At her last docking with the Port Authority, she was responsible for a contracting program of over $1 billion annually.

Frank still thinks big. The Transition Network now reaches over 4,000 women in 44 states through its online newsletter, memberships, and workshops. Members range in age from their late 40s to 80-plus. Some women are retired. Others work part time or full time.

Membership growth has been spurred by a new book by the Transition Network and Gail Rentsch, a founding member of the group, called Smart Women Don’t Retire-They Break Free. It’s a practical guide for boomer women searching for what’s next.

The group’s $500,000 annual budget is pieced together through donations from members and sponsors such as Fidelity Investments, the New York State Health Foundation, and the New York Times Foundation, plus support Frank received after being named a fellow of the non-profit Ashoka in 2006 for her lifetime of social entrepreneurship, particularly the Transition Network’s development.

Frank came of age as a feminist in an era when a woman was encouraged to get an education and use it to further her husband’s career. “My mother actually told me not to show my intelligence if I wanted to get a man,” she recalls. That is one piece of maternal advice Charlotte Frank ignored—to society’s benefit.