Charcloth: Wander over to Dick Gaughan's pages Clicky and look at the "Happy!" file. You may get some ideas. The actual File has about 50 times as much material. Let me know if I can help with any parrticular event or song. Then for fewer (but still many) but in-depth historical references to US folksong, check Manfred Helfert's excellent History In Song.

The "Happy!" file tells me Jenner's 1st innoculation was May 1, 1796 and the smallpox vaccine was made generally available Jan 21, 1799.