Bill was born to Anne Minor Dent and William Armstrong Percy, II, of the Mississippi Percy family. His mother was raised by her widowed uncle, the distinguished Memphis lawyer Dent Minor, scion of 17th-century settlers of those names in Maryland and Virginia. Dent's great-uncle John B. Minor taught law at the University of Virginia from 1845 to 1895 and served for decades there as dean of the Law School.
After graduating as valedictorian of Middlesex School (in Concord, Massachusetts) in 1951, Percy went to Princeton University, where he entered the Special Program in the Humanities. There, he struggled with the rejection and persecution of gays during the McCarthy years. At a time when conscription was still in effect, he volunteered for the U.S. Army. In his military stint, Percy studied Norwegian at the Army Language School. He worked as a French interpreter on loan to the Central Intelligence Agency on the island of Saipan.
Following the completion of his military service, Percy completed his B.A. in 1957 at the University of Tennessee. He spent a year obtaining a Certificato from the University of Naples. He went on to earn an M.A. from Cornell University, followed by an A.M., and in 1964 his Ph.D. from Princeton.
Percy taught at the University of New Orleans, Louisiana State University, and the University of Missouri at St. Louis for two years each. In 1968 he moved to the University of Massachusetts at Boston. After gaining tenure and promotion to full professor there, in 1975 Percy "came out" to colleagues. He joined the fight for equal rights for gays in 1982 after meeting Charley Shively. Three years later, Percy began publishing spectacular with two centerfolds in the very radical Gay Community News in gay studies.
Soon after, Percy served as the other associate editor with Warren Johansson of the Encyclopedia of Homosexuality (1990), which won six prizes and has recently been reprinted by Rutledge, costing $500 for the two volumes.
Paul Cartledge, of the University of Cambridge, described Percy's Pederasty and Pedagogy in Archaic Greece (1996) as the first work to try to go beyond Kenneth Dover's groundbreaking Greek Homosexuality. Dover's work, influenced by pseudo-Freudianism, was very homophobic.
At the time he published Outing: Shattering the Conspiracy of Silence co-authored with Warren Johansson (1994), Percy announced that he was offering a bounty of $10,000 for the person who successfully "outed" a living American cardinal, a sitting justice of the U.S. Supreme Court, or a four-star officer on active duty in the U.S. military. In light of the 2003 Supreme Court decision that decriminalized sodomy (Lawrence v. Texas), he amended his bounty offer to exclude a Supreme Court justice, but increased the bounty to $20,000 for a cardinal or a four-star officer., but after the military shaped up, he increased the offer to $30,000 for a living American cardinal.
Percy frequently contributes to The Gay and Lesbian Review Worldwide, published and edited by Richard Snyder. Like the Gay Community News before it, it is published in the South End of Boston, the gay neighborhood where Percy rehabbed 8 buildings. It is arguably the best gay periodical in the world, an honor once claimed by the Gay Community News.
In an ill-advised act of generosity, Percy had the graduate student who did most of the tedious work, Arnold Lelis, put his name first on the book about Roman ages of marriage. It got little attention. After about a year, Percy telephoned Thureon Sheidel, a leading expert in the field, to tell hum that he should read it because his own opinions were erroneous. A great deal of discussion ensued thereafter on the Princeton'/Stanford Working Papers in Classics. Thereon Sheidel tried to admit as few as possible of his errors. Since then, Percy posted on his own website a great many more refutations of Sheidel's work. The triumvirs, Saller, Shaw, and Sheidel persist in maintaining that Roman males married around age 28 instead of 18 to females of 18 instead of 143. In fact, of all ancient peoples, only Greek males waited until about 30 to marry. In Sparta, they married females of 18, but in other free cities they married females from 14-16.