Led Zeppelin's second album was cut, appropriately enough, on the fly – it was written and recorded (in studios of varying quality) during multiple U.S./European tours in 1969. As a singer and lyricist, Robert Plant was growing by leaps and bounds, guitarist Jimmy Page was coming into his own as a producer, and the thundering rhythm section of John Paul Jones and John Bonham helped make Led Zeppelin II the band's heaviest (and first No.1) album.

As on their debut, the blues influence is undeniable on such tracks as “Whole Lotta Love” and “Heartbreaker,” but the acoustic-flavored “Ramble On” was one indication that the U.K. quartet were looking well beyond Willie Dixon and Howlin' Wolf. The hard rock landmark celebrates its 50th anniversary this week, and it's still as powerful as ever.

Get Led Zeppelin albums on CD and vinyl here. 

Listen to Led Zeppelin II on Spotify

Listen to Led Zeppelin II on Apple Music