1966: “rock ‘n’ roll” became “rock”

“But 50 years down the line, a case can be made that 1966 may have been the single most creatively expansive year of all. That was the year that “rock ’n’ roll” morphed into “rock,” the year that the 45 rpm single yielded to the 33 1/3 rpm long-playing album as the dominant medium for the music and the year that social and political issues became a regular topic of exploration among musicians looking beyond the next hit and aiming to exert a real impact on the world around them.”

— 1966: Rock ‘n’ roll’s most revolutionary year (Los Angeles Times)