Williamson's wife Barbara told The New York Times he died of cancer March 24 in Reno, Nev. He was 80.
The couple opened Sandstone on 15 acres in Topanga Canyon in 1969 and were forced to close it in 1973 because of financial problems. Williamson spent decades working in electronics before he and his wife moved to Nevada almost 20 years ago and opened a rescue center for tigers and other large cats.
At Sandstone, the Williamsons attempted to build a community based on the "self-actualization" theories of psychologist Abraham Maslow.
"We just knew that a traditional heterosexual marriage could not last, because two people could not give each other everything they need," Barbara Williamson said. "So we built a bigger marriage."
Sandstone's fans included the singer Bobby Darin, Daniel Ellsberg, the former U.S. military analyst who leaked the Pentagon Papers, and the writer Gay Talese. Talese's book on the sexual revolution, "Thy Neighbor's Wife," was published in 1980.
The Williamsons continued to have an open marriage until they moved to Nevada in 1994, Barbara Williamson told the Times in an interview this week. She said they were happy with their cats.
"They just really gave us a lot of satisfaction," she said.