Topographical map source?

My guess is the OP isn't interested in detailed level of topographic maps, the ones with trails and streams and forest service roads. Grades, curves, and drop offs on major highways through the mountains are more the focus.

Delourme and Benchmark books might be more detailed than needed, though I do like them.

I have bought folding 'sports' or 'adventure' maps locally in various the Western states.

One clue that is present even on official state highway maps (do they print such things anymore?) - National Forests and National Parks are shown in a distinct color. Those almost always are in the mountains. At a first approximation, if a road passes through such an area, it is mountainous. If it passes between two such areas, it is likely to be in a valley between two ranges. Another clue - scenic route designation.

I'd suggest studying online sources such as GM with terrain to identify areas of interest/concern. Then look at the map rack in stores along the route (yes, even groceries and gas stations), to see which gives the most information on those areas of interest.

Many National Forest websites now offer topo maps as a free PDF download. 1" = 1 mile, the quads are 8.5x11 so you can print them on your home printer. Works better on photo paper, as regular paper will bleed a little bit and the details may be fuzzy. These are the FS in-house versions of the USGS maps, more frequently updated then the USGS originals.

I use the phone app Backcountry Navigator. Costs $10, and you can access various editions of topo maps, aerial photography, marine charts for free. Other more detailed and specialty maps are available for a subscription fee.

You can save an area to use off line, and it uses your phone GPS to show your location, makes tracks and waypoints.

Avenza PDF Maps app is free, and you pay for maps. Most USFS forest visitor maps and topo maps are available a lot cheaper than the paper versions. USFS MVUM maps are free (that was part of the deal when the FS contracted with Avenza to provide maps), some of the NPS visitor maps are free. Again, uses the phone GPS to track you on the map.

While online you can get topographic information from Google Maps - just turn on the terrain mode. Sat view and streetview give you more details.

Garmin offers an annual all you can eat topo product calls BirdsEye Topo. It works with a bunch of their GPS receivers (but only the one you choose), as well as the PC based Basecamp software. You pay $30/yr for access but you can download and keep all the maps you want and they continue to work after your subscription is up.

They are scalable USGS and Canadian government maps, plus have fun stuff like trails, landmarks and campsites labeled on them.

You can view and download the USGS maps for free here. They're not laminated, and maybe not the most convenient for route planning, but the price is hard to beat.

Delourme and Benchmark are similar to the Canadian Backroads series.

DeLorme sells a topo version of their map program: TOPO North America:

DeLorme

We have purchased DeLORME Atlas's for the individual states we frequent. They are in a book format and the size is about 11"x 15". The books also include listings of Campgrounds, scenic Drives, golf Courses, and many other Gazetteer items.

For recreational navigation planning, we use Benchmark Maps in the western USA. The maps are set up with topo and recreation sections that show public lands, campgrounds, back country roads, and many points of interest that most locals don't seem to know about too.

If a map shows a road, we've found as long as it is dry, we don't have problems with our small class C and toad. The problem is you need a different book for each state. We've got the full set. If comparing to DeLorme's Atlas and Gazetteer, we find the DeLorme product more difficult to read but it seems to have greater detail. The unfortunate part of the DeLorme product is we find many roads that are there, but are not suitable for RV use.

If you want an online topo map to play with, drop on over to gaiagps.com and play with their online map. We use the app for back country exploring with an Ipad in our Jeep. Not a free app, but does everything we need for our desert explorations here in Nevada.