The music industry can thank Glenn Miller's record label for the idea of gold records. Seventy-five years ago today, his song about a train trip became the world's first solid-gold hit.

"Chattanooga Choo Choo" is about a man going home, and promising his sweetheart he'll never roam. By February 10, 1942, more than 1.2 million copies of the song had been sold — and that was no small thing, the biggest seller in years. The record label, RCA Victor, celebrated by presenting Glenn Miller with a trophy during a live radio broadcast.

"I think everyone listening in on the radio should know, Glenn, it actually is a recording of 'Chattanooga Choo Choo,'" announcer Paul Douglas explained to Miller on air. "But it's in gold, solid gold, and is really fine."

Miller's honor started a self-congratulatory tradition of labels awarding their own artists framed gold records. Then, as rock and roll's rising popularity changed the record industry, new trade organizations formed, according to music historian Robert Oermann.

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Published by NPR on February 10, 2017: Written by Mike Miller