He was perhaps the first transgender man to publicly identify as gay,[2] and is largely responsible for the modern understanding of sexual orientation and gender identity as distinct, unrelated concepts.
[3] Sullivan was a pioneer of the grassroots female-to-male (FTM) advocacy movement and was instrumental in helping individuals obtain peer-support, counselling, endocrinological services and reconstructive surgery outside of gender dysphoria clinics.
[4] Sullivan first started keeping a journal at the age of 10, describing his early childhood thoughts of being a boy, confusing adolescence, sexual fantasies of being a gay man, and his involvement in the Milwaukee music scene.
[1] By 1975, Sullivan identified as a "female-to-male transsexual"[4] and it "became apparent" that he needed to leave Milwaukee for somewhere where he could find "more understanding" and access hormones for his transition.
[7] Upon arrival in San Francisco, Sullivan began working as a secretary at the Wilson Sporting Good Company, where he was employed as a woman but cross dressed as a man much of the time.
[4][5] In his personal life, Sullivan lived as an out gay man, but he was repeatedly denied sex reassignment surgery (SRS) because of his sexual orientation and the expectation of the time that transgender people should adopt stereotypical heterosexual opposite-sex gender roles.
In his final years he participated in AIDS drug trials, finished his book on Jack Garland, and continued to nurture the FTM group and Historical Society.
[5] He was the first FTM peer counselor at the facility and worked directly with gender-questioning AFAB clients; in 1980, Sullivan published one of the first guidebooks for transgender men, "Information for the Female-to-Male Crossdresser and Transsexual", which drew on his experiences volunteering at Janus and included some of his earlier publications in the newsletter of the Gay People's Union in Milwaukee.
[4] From July 1979 to October 1980, Sullivan edited The Gateway, a newsletter with "news and information on transvestism and transsexualism"[14] that was circulated by the Golden Gate Girls/Guys.
According to Megan Rohrer, Sullivan "transform[ed] Gateway in a way that [would] forever change FTM mentoring" because trans people could still obtain information on how to pass without having to attend group gatherings in person.
Under Sullivan's leadership, the get-togethers comprised a racially and sexually diverse membership, and were first modeled after other transgender social groups, taking place in bars and restaurant locations, but ultimately moving in 1990 to the Metropolitan Community Church in the Castro District.
The day after his death, a previously scheduled meeting became a makeshift memorial, attended by community members and friends, including Kate Bornstein.
[25] Through his work at the Janus Information Facility, Sullivan was connected to trained psychiatrists and psychotherapists like Walter Bockting, Ira B. Pauly, Paul A. Walker, who utilized his knowledge in their clinical research and invited him to medical conferences.
[27][28] The SNM is the first U.S. national monument dedicated to LGBTQ rights and history,[29] and the wall's unveiling was timed to take place during the 50th anniversary of the Stonewall riots.