There was a documentary 10 years ago about the history of the band. IIRC the band's first drummer was very talented but for whatever reason wasn't working out. The drummer had an unusual role for rock drummers -- he was actually kind of the "frontman" in the sense he would handle the audience patter, introducing the band, etc.
They found Peart working in his uncle's animal feed shop out in the countryside. He was an amazing drummer, technically speaking. Unlike his predecessor, Peart seemed to be a total introvert, and also didn't seem to mesh well with Lee and Lifeson (best pals since middle school). Nevertheless, he proved himself to be a creative leader, writing many of the band's most memorable songs, and crafting lyrics with meaning that go beyond what most hard rock bands were putting out at the time (see 2112 and Moving Pictures).
He took a long hiatus from music about 15 or 20 years ago after the deaths of several family members, and toured North America on his motorcycle. I always wondered about that trip, and what he was able to discover.