Sorry for taking so long to get back this thread - I've been having trouble accessing Bike Forums lately. Anyway, the USGS maps are good for finding road routes, but should
never be relied upon alone. Back them up with a recent road map. The USGS maps are seldom updated, and while this won't be a big problem in the middle of Vermont, it will get you into trouble in most populated areas.
Fixed gear sounds like a lot of fun, actually. Are you doing a loaded tour and stealth camping, or are you traveling light? I will admit that the former does seem borderline crazy, unless you're riding a fixed/free with a lower gear on the freewheel. And even then, yow! Expect to walk up a lot of hills
.