It was 44 years ago that...

Since someone eventually got around to Pet Sounds, I'll add a single (rather than an LP):

Chuck Berry's 1955 release, "Maybellene", at which time - it could be argued - Rock n Roll is born.

Marty

One could also argue that Little Richard's "Tutti Frutti" released in 1955 impacted rock and roll much more.

Little Richard began recording in 1951, 4 years earlier than Berry.

He is widely recognized as the performer who transitioned rhythm and blues to rock and roll.

Well if you wanna play that game,Rock Around the Clock by Bill Haley and the Comets started the RocknRoll revues that started carrying the sound through out the USA. RocknRoll in the south started breaking down racial barriers in the south.
But to get back to the original posters question
Srgt. Pepper was using new ways to record @ the time,heavily influenced by drug use which was taking off in the summer of love.
Bitches Brew fused Jazz and electric instruments in a raw nervy way making most jazz musicians sit up and take notice.

Jimi Hendrix "Are you Experienced"

Jimi Hendrix "Are you Experienced

I remember buying it the first week it was out. Used it to terrorize my parents along with The Velvet Underground.