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View series: The United States: a territorial history

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The Northern Frontier and the Oregon Territory

This map is part of a series of 20 animated maps showing the history of The United States: a territorial history.

During the negotiations for the Treaty of Paris in 1783, the American and English delegations had erred in placing the source of the Mississippi further to the north, thus creating uncertainty about the frontier between the two countries in the area around the Lake of the Woods.

Further to the west, tracing the outer edge of the Louisiana Purchase, the border ran along the Missouri River Basin. 

To overcome these ambiguities, a new line was drawn in 1818. It followed the 49th parallel from the Lake of the Woods to the Continental Divide in the Rocky Mountains.

For the area west of the Rockies, the two parties agreed to establish joint control over the Oregon territory, and fixed its southern frontier with Spain at the 42th parallel.  

The region’s rich natural resources, and in particular the vast number of animals that could be hunted for fur, led to strong competition for control of the territory between the Canadian Hudson Bay Company and the American settlers who, in 1811, had founded the trading post of Astoria at the mouth of the Columbia River.

In the 1840s, the American settlers set up trading posts mainly along the coast of Puget Sound and in the Willamette Valley. As the majority group in the colony, they called for Oregon to become part of the United States.

The negotiations were blocked for a while over claims for Vancouver Island and Puget Sound, because of their strategic importance for each party. The treaty signed on June 15, 1846 compromised by giving Puget Sound to the United States and Vancouver Island to the British.