Happy birthday, one day late:
1949: The 45-rpm record is introduced by RCA. Can rock 'n' roll be far behind?
[ . . .]
More important, though, was the timing. When rock 'n' roll started taking off in the mid-'50s, the 45 proved a perfect format for this music. With one song per side (the "A side" being the projected hit and the "B side" being filler, which often became the actual hit), the 45 had the distinct advantage of being affordable for most young fans.
God, I feel old. You can tell a lot about people today by what they have on their iPods. The version of that when I was young was the stack of 45s we carried around with us from party to party. And what we have lost by not being able to talk about "B sides" anymore. Just think what that would add to the presidential-primary conversations.