According to May Pang's book Instamatic Karma, The Beatles officially broke up at Disney World.

"When John hung up the phone, he looked wistfully out the window. I could almost see him replaying the entire Beatles experience in his mind.

He finally picked up his pen and, in the unlikely backdrop of the Polynesian Village Hotel at Disney World, ended the greatest rock 'n' roll band in history by simply scrawling John Lennon at the bottom of the page."

(This just breaks my heart.)