On important influence on the GD's jam style's not mentioned:

Before the Grateful Dead's hyper-extended electric jams, there was the very-similar "East-West" by the Paul Butterfield Blues Band. It filled a full-side of the PBBB's eponymous LP, & tended to be even longer at live shows. The Butterfield Band moved to the bay area right around when the Dead hit their jam stage. As the basic Butterfield's idea of a blues-rock band doing long jams was an inspiration, so Mike Bloomfield's constantly-searching, rule-breaking improvisational guitar style is the template for Jerry's most "far-out" not-quite-earliest guitar work. Granted, Jerry ran with it, Mike didn't, but please, a tip-of-the-hat to this crucial turn the road.