1765 as the name of a large river in the west of North America, probably the modern Columbia; a word of uncertain and disputed origin. It seems to be of Algonquian origin. In the U.S. it came to be applied to the northwest generally. From 1848 as the name of a U.S. territory, admitted as a state 1859. The Oregon in Pennsylvania was named for the western territory. Related: Oregonian.

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Definitions of Oregon from WordNet

Oregon (n.)
a state in northwestern United States on the Pacific;
Synonyms: Beaver State / or / Ore.