My favorite atlases of western states are the ones by Benchmark - and not just because some of my former students helped produce them. They are a co-production by Allan Cartography of Medford, Oregon (who also make Raven Maps, see below) and Eureka Cartography of Berkeley, California.
The maps have beautifully rendered topography and meticulously researched cultural features such as roads. They show land ownership clearly (very important in many areas, especially the desert) and an intelligent selection of features of interest.
The scale is too small to use for hiking, but they are the all-around best maps to plan driving trips in the west. Most importantly, they will help you to understand the landscape around you as you travel. I always have one with me and consult it frequently on my long trips.
The Benchmark Road and Recreation Atlas series now covers eleven states, essentially the entire west from the Rockies to the Pacific coast. I would love to see them add Alaska, Hawaii, western Canada, and Baja California, but that seems unlikely. I also think California should be offered in two volumes at a larger scale (also not likely - DeLorme recently combined their two volumes into one).
All Benchmark Atlases highly recomended