Sullivan was a founding member and board member of the GLBT Historical Society (formerly the Gay and Lesbian Historical Society) in San Francisco. His personal and activist papers are preserved in the institution's archives as collection no. 1991-07; the papers are fully processed and available for use by researchers, and a finding aid is posted on the Online Archive of California. The Historical Society has displayed selected materials from Sullivan's papers in a number of exhibitions, notably "Man-i-fest: FTM Mentoring in San Francisco from 1976 to 2009," which was open through much of 2010 in the second gallery at the society's headquarters at 657 Mission St. in San Francisco, and "Our Vast Queer Past: Celebrating San Francsico's GLBT History," the debut exhibition in the main gallery at the society's GLBT History Museum that opened in January 2011 in San Francisco's Castro District. Sullivan lobbied the American Psychiatric Association and the World Professional Association for Transgender Health for them to recognize his existence as a gay trans man. He was determined to change people's attitudes towards trans homosexuals but also to change the medical process of transition by removing sexual orientation from the criteria of gender identity disorder so that trans men who are gay could also access hormones and surgery, essentially making the process "orientation blind". In June 2019, Sullivan was one of the inaugural fifty American “pioneers, trailblazers, and heroes” inducted on the National LGBTQ Wall of Honor within the Stonewall National Monument (SNM) in New York City’s Stonewall Inn. The SNM is the first U.S. national monument dedicated to LGBTQ rights and history, and the wall’s unveiling was timed to take place during the 50th anniversary of the Stonewall riots. In August 2019, Sullivan was one of the honorees inducted in the Rainbow Honor Walk, a walk of fame in San Francisco’s Castro neighborhood noting LGBTQ people who have "made significant contributions in their fields."