The Great Hall / Long Hall Plummer Park was completed in 1938 as part of the Works Progress Administration (WPA) and countywide efforts to expand park space during the Great Depression.

When West Hollywood became a city on November 29, 1984 , Plummer Park is where the country’s first openly lesbian mayor and four other councilmembers were sworn in.

At the height of the HIV/AIDS epidemic, from 1987-1996, the facility in Plummer Park hosted the meetings of the local chapter of the prominent AIDS advocacy group ACT UP (AIDS Coalition to Unleash Power), serving as the backdrop to unprecedented campaigns for greater visibility and more effective treatment. The group was instrumental in compelling the federal government to respond to the HIV/AIDS crisis through new research and healthcare programs.