It was forty years ago today that Led Zeppelin IV (AKA “Zoso”) was released. Lacking the group’s name or a title, just symbols chosen to represent each of the band members (and never intended to be read as “Zoso”), the album sold huge right out of the gate. It entered the UK charts at #1 and remained a best-seller for well over a year. Although it never topped the US charts (it peaked at #2) it has always been the band’s most popular effort, and includes their best-known, most loved song, the eight minute rock anthem “Stairway to Heaven.” It’s on virtually every “top whatever” rock and roll lists you can name, normally in the first ten items.

Interesting to note that three outtakes from the Led Zeppelin IV IV recording sessions, “Down by the Seaside,” “Night Flight” and “Boogie With Stu” were later included on the sprawling double album Physical Graffiti in 1975.

Below, Led Zeppelin perform “Black Dog” and “Misty Mountain Hop” at Madison Square Garden in 1973.