1. On September 20, 1867, the United States formally took possession of Alaska from Russia, marking the end of Russian colonization and the beginning of American control over the territory.

2. September 20, 1902, marks the opening of the Alaska-Yukon-Pacific Exposition, a world's fair held in Seattle, Washington that highlighted the gold rush in Alaska and the Yukon.

3. In 1943, on September 20, the US Army activated the Alaska Highway, a feat of engineering that connected the contiguous United States to Alaska via a road network starting in Dawson Creek, British Columbia and ending in Delta Junction, Alaska.

4. September 20, 1958, marks the official opening of the Trans-Alaska Oil Pipeline, a 800-mile pipeline that runs from Prudhoe Bay in northern Alaska to Valdez in southern Alaska and transports roughly 25% of the US's domestic oil production.

5. September 20, 2016, saw the largest earthquake in the world that year when a 6.9 magnitude earthquake hit the coast of Alaska, causing minor damage but no reported fatalities.