Kesey had flown to New York in November 1963 with his wife Faye and Prankster George Walker to attend the Broadway opening of One Flew Over the Cuckoo's Nest. He also managed to see the 1964 New York World's Fair site under construction. Kesey needed to return to New York the following year for the publication party for his novel Sometimes a Great Notion and hoped to use the occasion to visit the Fair after it opened. This plan gradually grew into an ambitious scheme to bring along a group of friends and turn their adventures into a road movie, taking inspiration from Jack Kerouac's On the Road. As more Pranksters volunteered for the trip they soon realized they had outgrown Kesey's station wagon, so Kesey bought a retired yellow school bus for $1,250 from Andre Hobson of Atherton, California. The license plates read "MAZ 804". Hobson had already added bunks, a bathroom, and a kitchen with refrigerator and stove for taking his 11 kids on vacation.
The Pranksters added many more customizations, including a generator, a sound system (with an interior and external intercom), a railing and seating platform on top of the bus, and an observation turret coming out the top made from a washing machine drum fitted into a hole cut in the roof. Another platform was welded to the rear to hold the generator and a motorcycle. The bus was painted by the various Pranksters in a variety of psychedelic colors and designs. The paint was not day-glo (which was not yet common in 1964) but primary colors, and the peace symbol wasn't yet evident. The word 'Sunshine' was written in blue, but it was too early to refer to orange sunshine LSD or Kesey's not-yet-conceived daughter Sunshine.
The bus was named by artist Roy Sebern, who first painted the word "Furthur" (with two U's, quickly corrected) on the destination placard as a kind of one-word poem and inspiration to keep going whenever the bus broke down. The misspelled name is still often used, as in Wolfe's book.
The original bus's last journey was a trip to the Woodstock Festival in 1969. Once its historic trips had come to an end the bus was gutted and used around the Kesey's farm in Oregon until at least 1983, when it was mentioned and pictured in an article in the May–June Saturday Review. It was eventually parked in the swamp on Kesey's Farm, where it deteriorated over the years.