Left a map of Alaska over a century before the official discovery. From the Wytfliet atlas of 1597. Right the same area on a modern map (source)
According to Wikipedia, in 1732 the first Europeans explored Alaska. But the Wytfliet atlas of 1597 already provides a accurate deacription of Alaska.
In the north it has the large mouth of the Mackenzie river, first reached by Alexander Mackenzie 1789. The Brooks Mountain chain is called "Bergi Regio" what sounds like the Dutch "Bergige Regio" (mountainous region). The large river below looks like the Yukon.
The origin of the cartographic data about Alaska and parts of Canada is a mystery.
It is usually assumed that the first European boat to reach Alaska was the Russian St. Gabriel on August 21, 1732. In 1741 Vitus Bering led an expedition for the Russian Navy. After his crew returned to Russia with sea otter pelts judged to be the finest fur in the world, small associations of fur traders began to sail from the shores of Siberia towards the Aleutian islands.
The first permanent European settlement was founded in 1784. Between 1774 and 1800 Spain sent several expeditions to Alaska in order to assert its claim over the Pacific Northwest. These expeditions gave names to places such as Valdez, Bucareli Sound, and Cordova.
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