Final answer:
Rhythm and blues (R&B) was the most influential style in the development of fifties mainstream rock, leading to the creation of rock and roll. This new sound was marked by a combination of musical influences and captivated teenagers, contributing to social and cultural shifts in the United States.
Step-by-step explanation:
The style of music that was the most influential in the development of mainstream rock in the fifties was rhythm and blues (R&B). This genre, predominantly created by African American artists, was a combination of electric instruments with the sounds of gospel, blues, country, jazz, and R&B. It gave birth to rock and roll, a new sound characterized by its heavy rhythm, simple lyrics, and captivating melodies that primarily appealed to teenagers.
Artists like Little Richard, Chuck Berry, and Bill Haley were among the first to bring rock and roll to high levels of popularity. The genre became a significant component of the entertainment industry, influencing social interactions and diminishing racial barriers as both black and white teenagers enjoyed the music, despite initial resistance from many parents and conservationists. The rock and roll movement was responsible for cultural shifts and signified a growing generational gap between teenagers and their parents, who were less enthusiastic about the music and the values it seemed to promote.