“I wanna look like what I am but don’t know what someone like me looks like,” Lou Sullivan wrote in his diary, in the mid-sixties, when he was living as a teen-age girl in suburban Milwaukee. “I mean, when people look at me I want them to think—there’s one of those people that reasons, that is a philosopher, that has their own interpretation of happiness. That’s what I am.”

Sullivan’s diaries, which he began in 1961, at the age of ten, and continued until his death, from AIDS-related complications, in 1991, chronicle his quest to exist in the world as he was—and to partake in the happiness that might result when he did. The entries, which the editors Ellis Martin and Zach Ozma have collected in “We Both Laughed in Pleasure: The Selected Diaries of Lou Sullivan, 1961-1991,” track his evolution from a rebellious Catholic schoolgirl obsessed with the Beatles to a noted transgender writer and activist in San Francisco. Throughout more than twenty volumes—all of them chatty and tender, casually poetic and voraciously sexual—Sullivan workshopped his identity and his relationships, committing to the page an interior monologue of self-discovery that paralleled the gay-liberation movement, the burgeoning transgender-rights movement, and the AIDS crisis.

Sullivan was a gay trans man at a time when his sexuality and gender were seen as contradictory—a dual identity that couldn’t really exist. He wasn’t the first gay trans man, but, through his writing, activism, public speeches, occasional TV appearances, and dogged networking, he became one of the most visible. He lobbied the hidebound medical profession to recognize the existence of gay trans men and to remove sexual orientation from the criteria of gender-identity disorder. He organized support groups, edited newsletters, and, in 1980, wrote a book that billed itself “the handbook to address the needs of the female-to-male.” All the while, he made good on his adolescent vow “to keep a diary as long as I live,” in hopes that one day he would publish it—a record of “a phenomenon such as myself.”

Sullivan grew up in Wauwatosa, Wisconsin. His father, John, owned a hauling and moving company; his mother, Nancy, was a homemaker and sales clerk. Part of Sullivan aspired to be a good Catholic like the rest of his family: as a pre-teen, he declared in his diary that he loved Jesus and promised, “I’m gonna try to be beautiful in soul.” But already he had a subversive streak. He devoured pop music—the Beatles, the Rolling Stones, Bob Dylan—and enjoyed playacting as a boy. But if his music tastes were innocuous (his mother agreed that he could “maybe have a Beatles haircut before the last day of school”), he sensed that the stakes of his deeper rebellion—one that was as much existential as cultural—were far higher.

“I have a horrible temptation for sex acts,” he writes. “I’d never do these with anyone, though. I do play with myself, which is supposed to be wrong. But I can’t see it as wrong.” As a young child, he fantasized about prowling the streets at night dressed as a boy. He recorded the intensity of his adolescent sex drive (“I masturbated bout 5 times at work, drew dirty pictures, wrote dirty stuff”), along with his B.D.S.M. reveries and fascination with homosexuality. “My problem is that I can’t accept life for what it is,” he writes in a diary from the mid-sixties, “I feel there is something deep and wonderful underneath it that no one has found.” And what was underneath was his desire to be male.

Early on, this desire was intertwined with wanderlust. “I wish I was a boy! God, do I want so bad to roam,” Sullivan writes as a teen-ager, when he daydreamed about lighting out for Chicago or New York to live like his bohemian idols. After high school, he moved to Milwaukee, where, although still outwardly identifying as a woman, he found refuge in the local gay scene—its leather bars, S & M clubs, and grassroots activist groups. Sullivan joined the Gay People’s Union, an early gay-liberation organization, where he contributed articles to the group’s magazine and ran uncontested for the office of secretary. According to Brice D. Smith’s biography “Lou Sullivan: Daring to be a Man Among Men,” from 2017, Sullivan started wearing male clothes full time in 1973.

Like most other places in America at the time, Milwaukee provided scant access to transgender health care or information. “Wish there was a fucking gender clinic in this asshole city,” Sullivan writes. After he got a secretarial job at the University of Wisconsin-Milwaukee, he roamed the university library for books about gender identity, but, as Smith writes, “found no mention anywhere of individuals born female who identified as gay men.”

Some of what Sullivan initially learned about transgender culture came from an underground network of confidantes who found each other via the back pages of community newsletters and magazines. Loretta, a pen pal from Michigan whom Sullivan describes as “that Mich drag,” saw herself as cleaved in two by the gender binary: she considered her male half her “brother.” She answered the phone with a male voice that climbed into a feminine register when Loretta, supposedly a different person, took the line. “Gives you the willies,” Sullivan writes, of her split identities.

Sullivan’s own notion of identity aspired to be more fluid—at first, anyway. “I know how to be one of the boys, I never knew how to be a chick + I’m glad! Yet I think I can still be one of the guys + keep my identity as a girl, I hope, to make a pleasant combination,” he writes. That détente didn’t last. Sullivan began binding his breasts and made a penis from rolled-up socks, although those were poor substitutes for the body he wanted. “I’m so ashamed of my breasts + C [cunt],” he writes in one entry. When he finally worked up the nerve to buy a strap-on, he slept with it harnessed to his body all night.

Sullivan’s self-presentation made him a riddle to others, and sometimes to himself. A friend dubbed him “sissy butch”—a term he approved of, although at other times he called himself a transvestite. (At the time, the word “transvestite” denoted someone who presented as the opposite sex but didn’t want surgery; this was in contrast to a “transsexual,” who did want surgery.) Even as he understood the limitations of these labels, Sullivan seems to have craved their clarity: he felt at odds with other gay men (“how do I fit in?”), with feminists (“they always object to my dress”), with lesbians (“I like men”), with heterosexuals (“no way”), and with other transvestites (“they’re all male [to] female + put the make on me”). “I can’t relate to anyone,” he concluded.

In the late nineteen-sixties and early seventies, what today is called gender dysphoria didn’t have a diagnostic label. In 1966, Harry Benjamin, an endocrinologist, published “The Transsexual Phenomenon,” a landmark study of transgender identity. (According to Smith, Sullivan read the book obsessively, but was disheartened that it sidelined female-to-male, or F.T.M., cases.) A year later, Christine Jorgensen, a former G.I. who underwent sex-reassignment surgeries in the early nineteen-fifties, published a best-selling autobiography that enshrined her as the public face of what many Americans knew about transgender life.