Final answer:
Elvis Presley's career-defining moment was arguably his signing with Sun Records or his performance on The Ed Sullivan Show, which propelled him to stardom by showcasing his unique sound that blended various musical styles.
Step-by-step explanation:
The defining moment in Elvis Presley's career could be considered his signing of a record deal with Sun Records in 1954. This groundbreaking event led to the production of Elvis's first record, which featured a unique blend of musical styles, including gospel, blues, country, and R&B. However, Elvis Presley's widespread recognition and the pivotal point in his career could also be attributed to his debut on The Ed Sullivan Show, where despite the existing controversy surrounding rock and roll, his performance captured the hearts of a national audience and solidified his status as a music icon.
Elvis's single "Heartbreak Hotel" reaching number one on the charts in 1956 and his appearance on national television amplified his stardom, marking important milestones in his career. He became symbolic of the new rock and roll movement, merging different regional styles into what would become a signature sound that propelled him to stardom. His success despite the disdain from many adults of the time illustrates the generational divide and the transformative power of rock and roll as a cultural force.