Oregon is a state in the Pacific Northwest region on the West Coast of the United States. The Columbia River delineates much of Oregon's northern boundary along Washington state, while the Snake River delineates much of Oregon's eastern boundary along Idaho. The parallel 42° north delineates the southern boundary with California and Nevada. Oregon is one of only three states of the contiguous United States to have a coastline on the Pacific Ocean. Oregon was inhabited by many indigenous tribes before Western traders, explorers, and settlers arrived.