October 11, 1971 sees the release of John Lennon’s single “Imagine,” one of the most influential songs of the 20 century.

Lennon began writing the song while still a member of the Beatles, at a time when the band had achieved unprecedented popularity but struggled to cope with their new reality. The song’s idealistic, utopian lyrics were heavily influenced by Lennon’s wife, conceptual artist Yoko Ono. He would later assert that the “lyric and concept” were “straight out of Grapefruit,” a book of poetry by Ono, and she officially received a joint writing credit in 2017.

A little over a year after the Beatles broke up, Lennon recorded “Imagine” in a single session at his and Ono’s country estate, Tittenhurst Park, with producer Phil Spector. Unlike other Lennon releases from that era, such as “Give Peace a Chance,” “Power to the People,” and “Happy Xmas (War is Over),” the song did not contain an overt political message. Nonetheless, lines such as “Imagine all the people/ sharing all the world” embodied a radical utopian vision as well as the desire of Lennon and many others for an end to the Vietnam War and a return to the optimistic humanism that had defined much of the previous decade.

The song and its eponymous album were a massive success, ultimately the most commercially and critically successful of Lennon’s solo catalogue. Particularly in light of Lennon’s assassination in 1980, “Imagine” has become associated with both idealism and struggle. Since 2006, it has been played immediately before the dropping of the Times Square Ball on New Year’s Eve in New York City, and it was included in the closing ceremonies of the 2012 London Olympics as well as the opening ceremonies of the 2018 Olympics in Pyeongchang. The word “Imagine” is the only text to appear on the Strawberry Fields memorial to Lennon in Central Park, and Liverpool’s John Lennon International Airport uses as its motto a lyric from the song, “Above us, only sky.”