As noted above... GET THE MILEPOSTS book. It is upgraded every year and has virtually every stop along the way. If you are really board, you can read our travelogue of our vacation up and back on the Alaska Highway... Alaska Travelogue.
Lots of pictures and some brief narration of road conditions etc.
The start of the Alaska Highway is Milepost 0 in Dawson Creek, BC. There is an interesting visitor center/video presentation of the construction of the highway and you can learn about the explosion that leveled most of the town during road construction.
The signpost forest in Watson Lake, Yukon (milepost 635) is fascinating and is continuously growing. When we go again, we'll have a sign made up to take with us for mounting...
We were in a large motorhome and had little concern for wildlife as we camped, but a pop-up camper will be much more exposed. For example, as we were sitting and visiting with a road construction flag-person, she mentioned how often she had to run for her vehicle as bears would show up on site. We saw lots of bears... Brown (Grizzly) and black bears so be sure to practice safe food storage. There are plenty of other large mammals along the road that won't try and take your food.
If you travel at "night" (it stays light 'till 3 AM much of the summer months), some of the remote communities along the road operate with generator power during the day with no electricity at night so you could be sitting at the pumps until they fire up the community generator in the morning.
There are free places to camp all along the route. During construction of the original Alcan Highway, large construction yards were cleared and can be found easily along the route. The Canadian Provincial Parks are well maintained and inexpensive as well for the most part. The US National Wildlife Refuges along the Alaska Highway offer free camping too.
When we visited Danali National Park, we were lucky and got to see the big mountain the first day we were there... the rest of the week we scheduled there was cloudy and wet. The later in the season you go, the worse the mosquitoes will be... and they get big up north! If you go, be sure to see the dogs the National Park Service uses for winter patrols... very interesting, up close, and hands on the dogs is OK! Unless you camp in one of the remote campgrounds along the road, you will be required to take a bus into the deeper reaches of the park.
Photo taken from our inside our motorhome at campsite in Denali.
Oh yes... Salmon bake and sweet rolls the size of dinner plates are common. Be sure to eat at Silly Al's in Tok, Alaska. We made a circle trip as much as possible came back via Chicken, Alaska and Dawson City, Yukon. You may get stuck in a long of line of vehicles waiting on the ferry across the Yukon river. We went from west to east and had no line... the folks going from Dawson City into Alaska had long waits for the ferry.
It rains up north... almost every day on our trip so go ready wetness!
Have fun! I wish we were going again next year!