On July 5, 1954, Elvis Presley made his first commercial recording, "That's All Right," at Sun Studio in Memphis. He'd recorded "My Happiness" a year earlier in the same studio, but didn't much impress Sam Phillips, Sun's founder.
Many believe this recording ushered in the rock 'n' roll era, but black artists had been recording rock 'n' roll at Sun since 1950 and Bill Haley and his Comets were listed on Billboard charts with their song "Crazy Man Crazy" in 1953. This, however, was something new: a startling combination of country, gospel, rhythm and blues, and straight-ahead blues that was quite marketable in both the north and the south.
You can hear a little "That's All Right" on the Sun Studio home page. And while you're there, take the audio/video tour.