I use Benchmark Atlases in Montana and Idaho (
http://www.benchmarkmaps.com/). With pages torn out or copied from them, a gps, and our maps, you should be good to go. Sometimes you can get ahold of maps from smaller companies, such as Beartooth Publishing (
http://beartoothpublishing.com/) or Trails Illustrated (
http://www.natgeomaps.com/trailsillustrated.html), but their range is usually fairly limited.