Prior to American possession it was jointly claimed by Britain, Russia, Spain and the United States. By 1844, when Polk ran for President, Britain was the main contender . Of course, there were Indians living there as well. Nobody really owns land. You may be able to get a deed for a piece of land, but your deed is good only so long as the government that issued it holds power.
I can only guess the time frame you are asking about since you don't name it. It is Russia who first claimed the area we call Oregon.
It was owned by the Indians, but controlled by the Spaniards.
The Oregon territory was gained by the UNITED STATES of AMERICA from Britain. The Oregon territory was fairly large, which enabled the US to gain more resources and have more land for settlement. THESE FACTORS ARE THE EFFECTS OF THE ACQUISITION OF THE OREGON TERRITORY
Northwest Territory
Oregon Countrythe Oregon Countrythe Oregon Country
Britain
The Oregon Territory became part of the United States in the 1840's just before the Civil War. The discovery of the Oregon Trail led to many wagon trains and settlers going to Oregon Territory.
Oregon
Oregon
Russia, Spain and Great Britain also had claims on the oregon territory
1846
idek
Britain