This is one of many songs McLean worked up in the '60s when he made the rounds on the folk music circuit, playing clubs and festivals on the East Coast. He spent most of his time in New York's Hudson Valley, where he often performed with Pete Seeger. In 1969, McLean was a crew member on a sloop called the Clearwater, which Seeger sailed to pressure politicians into passing clean water legislation. During this time, McLean built a small following as he honed his skills. By the time he made his first album, he had written, rewritten, refined and discarded hundreds of songs, finally settling on 10. When he shopped it to record companies, he got rejection after rejection until Alan Livingston, formerly of Capitol Records, signed McLean to his new label, Mediarts.
In 1970, the album was finally released. Titled Tapestry, McLean beat Carole King to the name by a year. "Castles In The Air" was released as a single, but like the album, had little impact. Soon after, Mediarts ran into financial problems, putting McLean in rough waters. He kept writing songs for his next album, hoping something would work out, and they did: United Artists bought Mediarts and issued McLean's second album. That album was American Pie, catapulted McLean to the big leagues. "Castles In The Air" found a much bigger audience when his new fans dug into his catalog.