There are a few places on the Allagash to increase your chances of seeing moose, and Chisholm Brk is about as good as it gets. If you hit the backwater there in the early morning or go out for an evening paddle. We saw 8 in there one evening. The second best is the three channels that feed Round Pond and the pond itself.
One of my favorite spots is Sweeney Brk, there's a grassy area on the right that we've seen a female moose in there every time we've been thru there but one. Twice she had a calf.
The easiest ways to see moose is the obvious, be the first on the river that morning which used to be our goal, not so much anymore.
The last place, for early risers, is Musquacook Deadwater. One time we saw 4 just downriver of the Musquacook stream, they like that section of the river.
We've seen very few moose below the falls.
The highest count was 28, but 20 was the average in the first few years, the last few trips we've enjoyed the mornings in camp and haven't seen as many.