For a general overlay and highways I like the Recreational Maps put out by
www.gtrmapping.com. They make a two map set for Montana that shows all the recreational areas on a scale of 1 inch to 12 1/2 miles. This makes a good starting point to find what you want, then you can find the detailed map from one of the sources below.
All forests have their own maps. However, the scales vary and are usually not very easy to use hiking. I just looked at my Boise National Forest and it is mapped on a scale of 1:126720. Wilderness' are now publishing much better user friendly maps on waterproof paper and on a better scale, sometimes down to 1:24,000. You can get forest and wilderness maps at
www.fs.fed.us/maps for those areas adminsitered by the USFS. I have seldom used the Geologic survey maps as they too are usually high scaled.
www.usgs.gov
For Yellowstone, Trails Illustrated 201 covers the entire park and they also have the park broke down into 4 sections on maps 302, 303, 304, and 305. These are very detailed (1:63,360) with mileage between way points. Glacier NP has similar TI maps.
Just as a side note, I love being a AAA member. call your local office and they will send you highway maps, area AAA approved businesses, lodging, and meals info for your entire trip. Things to see and do along the way if you are driving as well as the area you are visiting. Also the AAA discount at rental cars is huge. No, I am not affiliated in any way, just found it immensely valuable if you put many miles on your car.
