After the release of Led Zeppelin III in 1970, some music critics, less than impressed with Led Zeppelin's brighter, folk-rock leaning sound on the LP, suggested any album would sell well as long as the band's name was on the cover.

Guitarist Jimmy Page decided to challenge that notion, proposing a different approach to the artwork on their fourth record. Names and titles were entirely stripped away and replaced by four of the most recognizable visuals in rock music.

"After all this crap that we'd had with the critics, I put it to everybody else that it'd be a good idea to put out something totally anonymous," Page told Trouser Press in 1977. "At first I wanted just one symbol on it, but then it was decided that since it was our fourth album and there were four of us, we could each choose our own symbol. I designed mine, and everyone else had their own reasons for using the symbols that they used."

Led Zeppelin IV, as the 1971 album became known, was never given an official title, even though the band's label was against it. The group wouldn't hand over the master tapes until the record company agreed to release the LP untitled. And aside from a production credit for Page, the inner sleeve included none of the member's names, just their symbols.

Page designed his symbol, the most complex-looking and one that fans assumed spelled something. “A lot of people mistook it for the word ZoSo," Page explained in The Making of Led Zeppelin’s IV." Which is a pity because it wasn’t supposed to be a word at all but something entirely different." Some theories have pointed to the symbol of Saturn, the planet that rules Page’s astrological sign of Capricorn; others have noted a potential drug reference in the resemblance to a pipe in the lower portion of the symbol. “Page once took me aside and said, ‘I’m going to tell you the meaning of this once, and then I shan’t ever mention it again,'" Robert Plant recalled in Led Zeppelin: In Their Own Words. The singer has since forgotten what the guitarist told him, and Page has never clarified the design.

Plant's symbol was also customized, though it was derived from a recognizable source. “My symbol was drawn from sacred symbols of the ancient Mu civilization, which existed 15,000 years ago as part of a lost continent,” Plant said for In Their Own Words. The term "Mu" was first introduced by archeologist Augustus Le Plongeon, who used the "Land of Mu" as an alternative name for Atlantis. But according to geologists, the existence of Mu is not considered to have any factual basis. The feather at the center of Plant's design is most often tied to the Ma'at, the Egyptian goddess of truth, justice and balance.

Bassist John Paul Jones kept his symbol simple. When flipping through the pages of Rudolf Koch’s Book of Signs, he came across the triquetra, which has Celtic and Gaelic origins. This particular version, intended to symbolize a person who possesses both confidence and competence, included a circle surrounding the triquetra. Drummer John Bonham selected his symbol from the same book: a design with three interlocking circles that represent the holy trinity: mother, father and child, which also mirrored Bonham's family status at the time with his wife, Pat, and son, Jason.

An additional symbol appeared on the inside cover in recognition of one of the album's two outside contributors, Sandy Denny, who sang on "The Battle of Evermore" — the only song Led Zeppelin ever recorded with a guest vocalist. A stack of three triangles was placed in the inner sleeve as Denny's symbol, though it isn't clear whether or not she selected the design herself.

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The symbols stuck around and reappeared over the years. Page's appeared on the inner cover of Plant's 1988 solo album Now and Zen, on which Page guests, as well as on the cover of Page's collaboration LP with the Black Crowes, Live at the Greek. A trippy version of Jones' triquetra can be seen on the cover of his debut solo album, 1999's Zooma, Bonham's symbol could be seen on the face of his son's drum kit and Plant still regularly used his symbol on tour merchandise.

Page was ultimately proven correct: Even without names and titles, Led Zeppelin IV dominated the charts and became the band's best-selling album of its career. "After a year's absence from both records and touring, I remember one agent telling us it was a professional suicide," he said. "We just happened to have a lot of faith in what we were doing."

Led Zeppelin Albums Ranked

Counting down every canonical Led Zeppelin album, from worst (relatively speaking, of course) to best.