I think you need a minimum of six weeks within Alaska itself. We hit Alaska on June 1st and were there for almost two months. That was a tad early because many things don't open for the season until mid-June. As Gary mentioned, the distances are huge! On our second trip we drove to Prince Rupert, took the Alaska ferry to Skagway, then went up to Dawson City in the Yukon Territory (five days there), crossed the Yukon River to Chicken AK, down to Tok, across to Fairbanks, down to Denali, Homer on the Kenai peninsula, Anchorage, and back through Tok and Valdez. We returned on the Alcan and down the Cassiar to Stewart and Hyder before Banff and the Icefields Parkway.
Getting a copy of the Milepost is mandatory so you know what you're looking at and see those big distances. There used to be one for the Pacific Northwest in addition to the Alaska edition. Also, there's a lot to see and do before even getting to Alaska. BC has the world's second largest aluminum smelter and you can tour it. They also had a number of different lumber-related mills we toured - oriented strand board, finger joining, lumber cutting, etc. The area that stretches from Seattle to Dawson City is an international park devoted to the Yukon gold rush. The Alaska pipeline is interesting. Between seeing all the manmade things and all that Mother Nature has to offer in the way of scenery, wildlife, glaciers, and such you'd be hard-pressed to see it all in a short time.
You might want to go to an army surplus store and get mosquito hats to protect yourself from Alaska's state "bird", especially at places like Denali. Alaska's a beautiful and interesting place so you should enjoy it. But, as the natives say, if the Fireweed is nearing the top of its stalk it's time to go south and that can happen pretty early. By the way, on two trips the only reservations we ever made were at the end of the ferry ride so we'd know there was a place to stay on arrival.
ArdraF
