Elvis
Elvis' music was heavily influenced by rythym and blues and gospel. Before he brought this music to the mainstream it was seen as "race music" and was popular mostly in the black culture. The reason Elvis became so successful with music that had been around for years was because his face was more "acceptable" to the mass white audiences. He was seen as a rebellious good boy and had a wide appealing image. He made it okay for the mainstream American popular culture to like the music that blacks had been listening to long before. Elvis' ability to break through prejudices and bring new music to the mainstream paved the way for other artists to follow.
Rock and roll is a genre characterized by rebellion, revolution, and evolution. Elvis started this movement with scandalous dance moves and loud music. His popularity allowed other artists to build off of what he had started. New artists found their voice and old artists found new audiences.