In 1899, a bar in San Francisco unveiled a new idea to capture customers' money. It was a coin-operated phonograph that would play a song on a wax cylinder. The sound was lousy, but that was the beginning of what we later came to know as the jukebox. In 1927, the first such vending machine with multiple records and amplified sound came out, and America fell in love with the jukebox.
Playing a song on a jukebox was much cheaper than buying records, much less the equipment to play them on. But the real genius was the machine's ability to tabulate how many times a song was played, and therefore how popular it was. Radio didn't keep track of such things in the 1920s, but caught on eventually. Meanwhile, the Mafia got involved, renting out machines and pushing songs from the studios they also owned. By the early 1940s, there were half a million jukeboxes around the country. But they really exploded after World War II, just in time to track the popularity of a new genre of music called rock and roll. Read up on the history of the jukebox at Smithsonian.
(Image credit: Ethan Long)