I draw that line near the "very" late 60's to very early 70's. Federal Homesteading was still open, however, (the "quality" of the land options was greatly restricted) by late 60's. There were still good T&M sites (15 acres) available (Trade & Manufacturing sites) for guiding or trapping, commercial fishing operations. Everything changed with the Fork-an pipeline construction.

We were then harvesting Alaska Mountain Goats, (two legally) for food up at the end of mineral road, out of Valdez, Alaska, every December.

I guess the line could be drawn marking the end of WW-II and the public access to the Alcan Highway.

Statehood was the political point. All subsequent major changes (ANSCA, pipeline, ANILCA, end of homesteading, etc) were a direct result of statehood.

You note WWII. The Cold War maintained and even grew the military presence. The next major war, which appears imminent, will be huge in Alaska.

Well, I missed out by a long shot, I was planning on settling in Alaska in the mid 70's but didn't.