<P> The Oregon Country was originally claimed by Great Britain , France , Russia , and Spain ; the Spanish claim was later taken up by the United States . The extent of the region being claimed was vague at first , evolving over decades into the specific borders specified in the US - British treaty of 1818 . The U.S. based its claim in part on Robert Gray 's entry of the Columbia River in 1792 and the Lewis and Clark Expedition . Great Britain based its claim in part on British overland explorations of the Columbia River by David Thompson and on prior discovery and exploration along the Coast . Spain 's claim was based on the Inter caetera and Treaty of Tordesillas of 1493 -- 94 , as well as explorations of the Pacific coast in the late 18th century . Russia based its claim off its explorations and trading activities in the region and asserted its ownership of the region north of the 51st parallel by the Ukase of 1821 , which was quickly challenged by the other powers and withdrawn to 54 ° 40 ′ N by separate treaties with the US and Britain in 1824 and 1825 respectively . Spain gave up its claims of exclusivity via the Nootka Conventions of the 1790s . In the Nootka Conventions , which followed the Nootka Crisis Spain granted Britain rights to the Pacific Northwest , although it did not establish a northern boundary for Spanish California , nor did it extinguish Spanish rights to the Pacific Northwest . Spain later relinquished any remaining claims to territory north of the 42nd parallel to the United States as part of the Adams - Onís Treaty of 1819 . In the 1820s , Russia gave up its claims south of 54 ° 40 ′ and east of the 141st meridian in separate treaties with the United States and Britain . </P>
in the early 1800s what four countries claimed land in oregon
Great Britain France Russia Spain