Bobby Owsinski wrote on his blog bobbyowsinski.blogspot.com an article about how stereo drun recording started which I thought was worth sharing. Originally, drum recording was always done in mono. Only two mics were used, an overhead and a kick drum mic. This changed when Glyn Johns, sound engineer of Led Zeppelin, accidentally panned the snare mic to the left and the overhead to the right. This ended up sounding great on the recording, so the band decided to keep it and recorded the rest of their music that way.
Read the full article here:
How Stereo Drum Recording Started