Along with the Milepost, as mentioned above, also get the Church's Camping guide. Together they will give you the most info as to where you might want to go.
Don't forget to check out all that Canada has to offer. We crossed at Sweetgrass, MT (Coutts, Alberta, CA) headed to Calgary and then on to Banff. The Ice Field Parkway (route 93)is a must see from Banff to Jasper. We also took the Yukon highway out of Whitehorse to Dawson City, YT, (another must see) then crossed the Yukon River on a free ferry, across the Top of the World highway to Chicken, AK and then on to Tok, AK. On the way back, we took the Alaska Highway out of Tok. I could go on and on, but this is just a start. Enjoy!!