The Allagash trip really divides into three segments: the lakes (which were
the old way to access the waterway), the upper river from Churchill Dam to
Round Pond, and the Musquacook Deadwater to the Town of Allagash. There are
several good guide books on the area. I used an old one from AMC on my
first trip. The lakes are lovely, but big and they can be windy. The first
couple of miles below Churchill Dam are Class 3 as I recall - fun, but maybe
it would be wiser to cache most of the gear below that bit. The section
from there to Round Pond has pretty good flow through the summer months.
However, once you are below the Deadwater, the river spreads out into a
braided network of shallow gravel channels and you can expect to drag your
boat quite a bit. The lower section is also where you can find Allagash
Falls - one of my kids favorite places.

Eric