One other resource that may make planning easier are the Benchmark Atlases and Maps. These are available for the western states. Seems REI only stocks the Maps and a limited selection of the atlases but you can get them elsewhere.
If you can't get the Benchmark atlases then DeLorme also publish atlases with similar detail although I did not find them as attractive and REI does not carry any for the western states.
These maps show all the public lands and attractions and provide a much better overview and local detail than any online resource I have found. Paper maps do go out of date so pay attention to the published date and try to get the most recent. However public lands generally don't change much and for planning purposes the goal is more to find likely places and then check the information.
While traveling off the beaten path it is wise to have paper map in addition to GPS devices because there is not always signal and online maps are not that great at providing an overview with enough detail.