ROCK N’ ROLL HALL OF FAME INDUCTION (1998).
According to John Phillips in a Bravo documentary, and Michelle Phillips in an NPR piece, the song was written in 1963 while they were living in New York. He dreamed about the song and woke her up to help him write it. At the time, the Phillipses were members of the folk group The New Journeymen which evolved into The Mamas & the Papas.
They earned their first record contract after being introduced to Lou Adler, the head of Dunhill Records, by the singer Barry McGuire. In thanks to Adler, they sang the backing vocals to “California Dreamin'” on McGuire’s album This Precious Time. The Mamas and the Papas then recorded their own version, using the same instrumental backing track to which they added new vocals and an alto flute solo by Bud Shank. McGuire’s original vocal can be briefly heard on the left channel at the beginning of the record, having not been completely wiped.The single was released in late 1965 but it was not an immediate breakthrough. After gaining little attention in Los Angeles upon its release, Michelle Phillips remembers that it took a radio station in Boston to break the song nationwide.By early 1966, the song peaked at #4 and stayed on the charts for 17 weeks.