The Oregon territory
The United States, Great Britain, Spain, and Russia claimed the Oregon territory, in other words, the Oregon Country.
U.S. and Britain
The territory of the original 13 states was ceded by Great Britain under the 1783 Treaty of Paris ( ratified by the Congress of the Confederation on January 14, 1784, and by George III, King of Great Britain on April 9, 1784) Parts of North Dakota and Minnesota were ceded by Great Britain to the USA under the Convention of 1818 between the United States and Great Britain.
Great Britain agreed to withdraw its remaining troops from the unites states territory.
The United States did not pay for the southern half of the Oregon Territory but there was compensation for the assets of the Hudson's Bay Company in the territory ceded in 1846. Britain ceded the territory to the United States under threat of war even though the United States had few if any genuine territorial claims to the territory north of the Columbia River. It is also ironic that at the very time the United States was readying itself for war with Mexico it was also threatening war with Great Britain. Even more ironic that within 15 years the United States desperately needed the good will of Great Britain.
Russia,France,Great Brittian,and the United States
United States and Great Britain jointly controlled the Oregon territory.
The Oregon territory
Great Britain
Great Britain and the United States both wanted the northwest area that is now Oregon and Washington state. President Polk told Great Britain "54'40" or Fight." There was no fight, there was a compromise.
NO the French had contol of the Louisiana Territory
No, the last territory acquired by the United States was not the Oregon Territory. The Oregon Territory was acquired in 1846 through a treaty with Great Britain. The final addition to U.S. territory was the purchase of Alaska from Russia in 1867.