In 1996-7, the full professors were Paul Benacerraf, Sarah Broadie, John Burgess, John Cooper, Harry Frankfurt, Gilbert Harman, Richard Jeffrey, Mark Johnston, Saul Kripke, David Lewis, Alexander Nehamas, Scott Soames, Bas van Fraassen, and Margaret Wilson; Bob Freidin and Beatrice Longuenesse were associate professors; Elijah Millgram, Gideon Rosen, and Gopal Sreenivasan were assistant professors; and Sarah Buss was a lecturer. Barbara Herman gave the Carl G. Hempel Lectures (formerly the Three Lecture Series).
There were several major developments at Princeton during the 1990s. The first was the construction of Marx Hall adjoining 1879 Hall. Graduate seminars were no longer given in Firestone Library, but instead took place in the department's own purpose-built seminar room: 201 Marx Hall. Just as importantly, the members of the department were no longer spread over several buildings, but had offices next to each other in 1879 and Marx.
The second major development was the appointment of two senior women: Sarah Broadie in 1993, and Béatrice Longneusse in 1994. Up until the nineties, Margaret Wilson, who had joined the department in 1970, was the only woman to have held a senior appointment in philosophy at Princeton. Understanding why there are so few women in philosophy, and how that issue might be addressed, is an on-going research project of one of the senior women currently in the department.
The third major development was the appointment of Alexander Nehamas and Harry Frankfurt, both of whom joined the Department in 1990. Nehamas took up the Edmund N. Carpenter II Class of 1943 Professorship in the Humanities, the first person to hold the position. Towards the end of the nineties, he talked about his career in philosophy in the magazine Bomb. Nehamas explained that, from his family's point of view, he is a failure: "Greece was not and is not a country where an intellectual and academic career is considered proper. It's all right to be cultured and educated, but you are not really supposed to live off your education. You work; it's a mercantile society." Frankfurt, who turned 70 at the end of the decade, was celebrated with a conference and a book in his honor edited by his students, Sarah Buss and Lee Overton, Contours of Agency (MIT Press, 2002). In her review of the book, Nomy Arpaly recalled:
Reading it, I had to remember the conference, held by the authors, that helped inspire it. Under the auspices of Wake Forest University a cast of excellent speakers came to honour Frankfurt, who was approaching the age of seventy, in the way that philosophers do: by enumerating the many ways in which they thought he was mistaken. Frankfurt replied, making clear the many ways in which he remained unconvinced. Philosophy being a strange profession, there was not a dry eye in the lecture hall after this exchange. This book, too, is moving in the way it manages, implicitly but clearly, to convey the admiration and gratitude of the editors and contributors towards Harry Frankfurt, while demonstrating at the same time how warranted these sentiments are. (Nomy Arpaly, "Review of Contours of Agency" in Mind 2004, pp.744-747)
The fourth major development in the nineties was the establishment of the University Center for Human Values with Amy Gutmann as its founding director. By the end the decade, UCHV's presence was beginning to have a significant effect on philosophy at Princeton. The UCHV itself had an active visiting fellowship program that brought several philosophers from elsewhere to Princeton each year, and, in 1999, Peter Singer was appointed to the Ira W. Decamp Professorship of Bioethics. You can read about Singer's first few years at Princeton here. (Note the misrepresentation of Singer's views: "Dr. Singer has become widely known and reviled for his position that newborn humans are not sentient.")