Born in New York, Arthur Kleps was working as a school psychologist in 1960 when he had a strong visionary experience on 500 mg of mescaline sulfate, which he'd ordered through the mail. After sending Timothy Leary a copy of his Neo-Psychopathic Character Test, Kleps was invited to visit Leary, Richard Alpert, and Ralph Metzner, who had moved to the Millbrook Estate.

Four years later, Kleps was fired from his position after writing a paper about marijuana. He then bought a piece of property in the Adirondacks and founded the Neo-American Church. He played the role of "Chief Boo Hoo, Patriarch of the East" for the psychedelic church, a title intended to remind him not to take himself too seriously. The church sporadically produced a newsletter for its members called Divine Toad Sweat. Using LSD and peyote as sacraments, the church was loosely modeled after the Native American Church. After a long court case, the authorities eventually ruled that although Native Americans were allowed to consume peyote within the context of religious ceremonies (since such use was traditional), the Neo-American Church was not allowed to use peyote because, in their eyes, Kleps' new church was not sincere. The court characterized Kleps as attempting to use a religious smokescreen in order to bypass the drug laws.

In 1967, Kleps relocated to Millbrook, where Timothy Leary described Kleps as a "mad monk". He lived there for a year before it was dissolved due to police pressure in 1968. While living at Milbrook, Arthur Kleps was dosed one morning with a large amount of LSD and he underwent a mystical experience. He eventually documented his adventures there in his book Millbrook. Unfortunately, Kleps also was accused of having anti-semitic tendancies, and at one point was kicked out of the Netherlands on this charge. His supporters point out that his extreme anti-establishment views were not specifically anti-Semitic but anti-any-religion.