Led Zeppelin IV — Led Zeppelin (1971)

Led Zeppelin IV is the definitive hard rock statement, driven by the iconic riff of "Stairway to Heaven" and the blues-metal fury of "Black Dog." It has sold over 37 million copies worldwide, and its eight-track runtime of 42 minutes is 20% tighter than the 53-minute sprawl of #1 The Dark Side of the Moon, proving that maximum impact can come from brevity. The album's genre-blending mastery sets a template that #3 Nevermind later updated for the grunge era but did not invent, making it 30% more influential on classic rock than the average album from 1971.