"I think it's really curious that it's the Ivy League that has led the way," Tilghman said, noting that far fewer major research universities are led by women. "But it's been terrific. It's signaling that academia is a place where women really thrive."
Tilghman, 66, announced last month she would step down at the end of this academic year, explaining that the goals she had set for Princeton were either completed or "irreversibly on their way to being successfully done." That includes a $1.88 billion capital campaign that ended in June ahead of its financial target, and a substantial increase in financial aid as she continued the university's policy begun in 1998 of replacing student loans with grants. She's also proud of invigorating performing and creative arts highlighted by the creation of the Lewis Center for the Arts, named in 2007 after 1955 graduate Peter B. Lewis.
"It became clear to me that I was either going to start a whole new series of things, in which case, I was looking at another five years, or I was going to declare victory and turn the university over to the 20th president," Tilghman said during an hour-long interview in her brightly colored office at Nassau Hall, where the marble walls of the high-ceiling entryway are filled with hundreds of names of Princeton graduates who died in major wars, dating to the American Revolution. "The more I thought about it in those terms, the more I realized that the right decision was to allow someone with fresh eyes and a different perspective to assess where we were and decide the next step."
Her departure coincides with presidential openings in the last year at three other Ivy League schools, putting the leadership of half the nation's most prominent universities - its powerhouse brain trust of sorts - in flux at once.
Yale University's Richard C. Levin announced he would step down in June after a transformative two decades at the New Haven, Conn., campus. Jim Yong Kim left Dartmouth after three years to take over as head of the World Bank in July; provost Carol L. Folt has stepped in as interim president as the New Hampshire school searches for Kim's replacement.
And Paxson, an economist who had been dean of the Woodrow Wilson School of Public and International Affairs at Princeton, was appointed president of Brown University in Providence, R.I., in July.
But experts say having so many openings at once shouldn't create a problem for such highly resourced universities.
"These are the institutions that carry the reputation of American higher education," said Molly Corbett Broad, president of the American Council on Education. "They are . . . very strong academically and financially and should attract the very best people in American higher education."
David Warren, president of the National Association of Independent Colleges and Universities, acknowledged that it was unusual to have several presidents retiring simultaneously.
"There is certainly going to be some overlap in terms of the nominated candidates," he said.
Ivy League universities tend to look at leaders, such as provosts and deans, within their institutions or from other Ivies. Prominent state universities also have proved fertile ground, with two current presidents, Columbia's Lee C. Bollinger, and Cornell's David J. Skorton hailing from the University of Michigan at Ann Arbor and the University of Iowa, respectively.
A sitting president at another Ivy, however, isn't likely to be a choice, if history is any indication. Experts couldn't recall such a case. Presidents are so deeply engaged in fund-raising with their donor bases that it would be difficult to switch, especially if the schools were in close proximity, Warren said.
"There is a sense it wouldn't be collegial," Princeton's Tilghman added.
Princeton's student newspaper, the Daily Princetonian, reported last month that former Gen. David Petraeus, director of the CIA, was interested in becoming Princeton's president. He got his doctorate from Princeton's Wilson school.
But several experts said they would be surprised to see Princeton make such an unusual choice, given that university leadership was about persuasion, coalition building, and navigating relationships with faculty and donors.
"There's a difference between being a general, where you're in charge, and being the president of a university, which some have described as kind of like herding cats," said Ronald G. Ehrenberg, director of the Higher Education Research Institute at Cornell.
Princeton hopes to name its new president by late spring.
Tilghman is one of four current Ivy presidents with ties to the region. A native of Canada and a molecular biologist, she earned her doctorate in biochemistry from Temple University, then worked at the Institute for Cancer Research in Philadelphia. She was an adjunct associate professor at Penn before joining Princeton's faculty in 1986.
Others with local ties include Paxson, who earned her bachelor's degree from Swarthmore College; Harvard president Drew Gilpin Faust, a historian who earned her bachelor's degree from Bryn Mawr and her advanced degrees from Penn and who spent 25 years on Penn's faculty; and Gutmann, who was Tilghman's provost before coming to Penn in 2004.
One of the oldest research universities in the country, Princeton, with its stunning physical campus in central New Jersey, is one of the richest in the world. Its endowment, valued at $17.1 billion as of June 2011, the most recent figure available, is the highest per student of any university in the country. The campus serves about 5,200 undergraduates and 2,600 graduate students.
Tilghman became its president three months before 9/11, which she said proved a major challenge. The campus "came together as a university community to try and absorb what had just happened," she said. "That became a yearlong series of conversations, symposia, panel discussions, and sit-ins."
But her toughest challenge, she said, was getting the university through the recession. Princeton's endowment dropped 23 percent during six months, and the university cut 15 percent of its operating budget, or about $170 million.
"All of that had to be done without affecting the quality of the education of our students, and it had to be done without losing a single student based on their ability to pay," she said.
Princeton was the nation's first university to eliminate loans from financial aid packages and replace them with grants. Tilghman said she was proud to have been able to continue that commitment despite the financial pressures.
Early on in her presidency, Tilghman named several women to top posts at Princeton, drawing criticism, which still puzzles her.
"What confused me is that some fraction of the pushback was coming from women students," she said, "which I couldn't understand for the life of me."
When she appointed a female replacement for Paxson at the Wilson school this year, "I didn't hear boo . . . I take that as a good sign."
Several years ago, Tilghman named a committee to look into why Princeton wasn't yielding more female candidates for prestigious Rhodes scholarships. The committee found that many men were applying - even those who didn't have the credentials - and very few women, she said.
"So it came down to a self-confidence issue," Tilghman said.
Princeton restructured its fellowship office and began identifying men and women who were strong candidates in their sophomore year, Tilghman said.
"That's all it took," she said, noting that three of the four Rhodes scholars from Princeton in the last year were women. "We really changed the way women were thinking about themselves."
Under Tilghman's leadership, Princeton also built a neuroscience institute, a new library, a new residential house to accommodate a larger student body, and a center for energy and the environment, and she started a center for African American studies.
Tilghman, an avid skier, tennis player, and Bob Dylan fan, said what she most liked about the job was interacting with so many different people and having the ability to solve problems, big to small, such as waiving a rule so students could reorganize furniture in their dorm space.
She, of course, could not fix everything. Tilghman held weekly office hours for students so she could hear what was on their minds.
"I had a student who came in and complained about the color of cheese served in the dining halls," she said. "I suggested to him that I was probably not the right person to have that conversation with."
She also taught while serving as president. This semester, she is co-teaching a course on genetics and public policy.
Tilghman said she was looking forward to her next step - a sabbatical and then a return to the Princeton faculty. She intends to remain in Princeton, where she has lived for 27 years and raised a daughter, Rebecca, a collections manager at the Metropolitan Museum in New York; and a son, Alex, a sound engineer who lives in Yardley.
"I'm not at all fearful of what it will be like when I'm not sitting at that desk," she said. "I'm looking forward to having a different quality of life, not better or worse, just different."
Contact Susan Snyder at 215-854-4693, email@example.com, or follow on Twitter @ssnyderinq.