Funeral arrangements were still pending for Kesey, who had been suffering from complications of liver surgery and had been hospitalized in Eugene, Ore.
Kesey's most notable work was "Cuckoo's Nest," which was turned into a successful Broadway play and then a 1975 film starring Jack Nicholson that won five Oscars, including the Best Picture award.
The inspiration for the book came from a blend of Kesey's experiences working in a mental hospital and multiple doses of hallucinogenic drugs that were popular at the time.
The New York Times said Saturday that it was while under the influence of peyote, a so-called "magic mushroom," that Kesey dreamed up the character of Chief Broom, a hulking American Indian inmate who turned the novel into a statement on repressive American culture in the early 1960s.
Kesey also wrote the novel "Sometimes a Great Notion," the story of an Oregon logging family, which gained mixed reviews but was also turned into a film.
Much of Kesey's notoriety, however, did not stem from his writing but from his exploits in the fledgling hippie movement of the mid-1960s. He and his cohorts experimented liberally with LSD and themselves became the subjects of a popular book, Tom Wolfe's "The Electric Kool-Aid Acid Test."
Wolfe's book chronicles the coast-to-coast road trips taken by Kesey and a group of friends known as the Merry Pranksters aboard a brightly painted bus that was aimed largely at attracting attention from passers-by.
Wolfe turned the bus trip into a pop-culture epic that inspired the notion of finding oneself among thousands of young people growing up during the increasingly turbulent decade.
Kesey was born Sept. 17, 1935, in La Junta, Colo., to dairy farmers Fred and Geneva Kesey. As a child, he and his family moved to Springfield, Ore., where his father founded a successful marketing cooperative for dairy farmers.
A popular high-school athlete in football and wrestling, Kesey went on to graduate from University of Oregon. He married his high-school sweetheart, Norma Faye Haxby, in 1956. He was the father of two daughters and two sons, one of whom, Jed, died in a 1984 automobile accident.