"California Dreamin'" is a song written by John Phillips and Michelle Phillips and was first recorded by Barry McGuire. However, the best known version is by The Mamas & the Papas, who sang backup on the original version and released as a single in 1965. The song is #89 in Rolling Stone's list of the 500 Greatest Songs of All Time. The lyrics of the song express the narrator's longing for the warmth of Los Angeles during a cold winter in New York City.

The song became a signpost of the California Myth and the arrival of the nascent counterculture era.

"California Dreamin' " was certified as a Gold Record (single) by the RIAA in June 1966 and was inducted into the Grammy Hall of Fame in 2001.

The song was written in 1963 while John Phillips and Michelle Phillips were living in New York. He dreamed about the song and woke her up to help him write it. Michelle Phillips enjoyed visiting churches, and she and John Phillips visited St. Patrick's Cathedral, which inspired the second verse of "California Dreamin’" ("Stopped into a church..."). John hated the verse, as he was turned off to churches by unpleasant memories of parochial school, but he couldn't think of anything better so he left it in. At the time, John and Michelle Phillips were members of the folk group "The New Journeymen", which evolved into The Mamas & the Papas.

...
Wikipedia