Rock and roll (often written as rock & roll, rock-n-roll, and rock 'n' roll) is a genre of popular music that evolved in the United States during the late 1940s and early 1950s. The origins of rock and roll include a mix of styles, mainly rhythm and blues and country music, with influence from gospel, jazz, boogie-woogie, electric blues, jump blues, swing, and folk music. While rock and roll's early elements can be heard in blues records from the 1920s and in country records of the 1930s, the genre did not acquire its name until 1954.
By the mid-1960s, rock and roll had developed into "the more encompassing international style known as rock music, though the latter also continued to be known in many circles as rock and roll". For the purpose of differentiation, this article deals with the first definition.