NEW YORK — Charles Reich, the author and academic whose “The Greening of America” blessed the counterculture of the 1960s and became a million-selling manifesto for a euphoric way of life, has died.

Reich’s nephew Daniel Reich said he died Saturday after being briefly hospitalized. Charles Reich, a longtime resident of San Francisco, was 91.

Reich was a popular Yale University professor and a respected legal scholar when a 39,000-word excerpt from “The Greening of America” ran in The New Yorker in September 1970, generating a massive volume of letters. The book was published a few weeks later and sold more than 2 million copies, making Reich a middle-aged hero for a rebellious generation.

“The Greening of America” presented American history as an evolution of consciousness, a three-part story. Consciousness I, dating back to the country’s beginnings, reflected a Jeffersonian society of individualism, virtue and suspicion of government. Consciousness II, which matured in the 20th century, believed in the “organization,” in technology and government and big business. The uprisings of the 1960s marked the dawn of Consciousness III, the triumph of compassion and imagination, an awakening enabled by sex, drugs and rock music.

He left Yale in 1974 and moved to San Francisco. He let his hair grow longer and began having relationships with men. In his 1976 memoir “The Sorcerer of Bolinas Reef,” he wrote that he had sensed he was gay since childhood. “I think I feared most the discovery and exposure of my secrets,” wrote Reich, who is survived by his nephew and by his niece, Alice Reich.