Which nation claimed oregon county in the early 1800s?

England.

Explanation:

Oregon County was first claimed by Great Britain, France, Russia, Spain, and the United States. However, France, Spain, and Russia gave up their claims through several treaties. On the other hand, the US and Britain agreed on a Treaty on the Anglo-American Convention of 1818 that established a joint occupation. Finally, the Oregon Treaty of 1846 would establish the British-American border at the 49th parallel.

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