In a new interview, out actor Anthony Rapp describes LGBT activist Harry Hay as revolutionary.

Rapp, who is best known for playing Lieutenant Commander Paul Stamets on the CBS All Access series Star Trek: Discovery, portrays Hay in HBO Max's upcoming docuseries Equal.

The series features a star-studded cast, including Cheyenne Jackson, Hailie Sahar, Isis King, Jamie Clayton, Keiynan Lonsdale, Samira Wiley, Sara Gilbert, and Shannon Purser.

Equal, which premieres Thursday, October 22, highlights LGBT rights pioneers.

Hay, who died at 90 in 2002, was a co-founder of the Mattachine Society, America's first sustained gay rights group, and the Radical Faeries, a gay spiritual movement. Hay has been described as “the father of gay liberation.”

Speaking with LGBT blog Instinct, Rapp said that he jumped on the opportunity to join the cast of Equal.

“I was like, 'absolutely,'” he said. “I believe so strongly in telling the stories of our history and what we can learn from the pioneers that came before us. So it was really, really meaningful.”

Referring to Hay's 13-year marriage to a woman, Rapp said that gay men in the 1930s “were not necessarily expecting themselves to live as they really were. But just to be willing to do that at that time was incredibly courageous and revolutionary.”

“I think it's important to recognize pioneers who came before us,” Rapp said. “I think it's incredible how much progress has been made.”