Nirvana, 1991. Smells Like Teen Spirit displaced Michael Jackson at #1 — the grunge-era inflection point.
From Wikipedia
Nevermind is the second studio album and major label debut by American rock band Nirvana, released on September 24, 1991, by DGC Records. It was Nirvana's first release to feature drummer Dave Grohl. Produced by Butch Vig, Nevermind features a more polished, radio-friendly sound than the band's prior work. It was recorded at Sound City Studios in Van Nuys, California, and Smart Studios in Madison, Wisconsin, in May and June 1991, and mastered that August at the Mastering Lab in Hollywood, California.