A state of the northwest United States in the Pacific Northwest. It was admitted as the 33rd state in 1859. Claimed by the United States after Capt. Robert Gray explored the mouth of the Columbia River in 1792, the area was further explored by Lewis and Clark in 1805 and was soon the site of fur-trading posts. The Oregon Country, a region encompassing all the land from the California border to Alaska and the Pacific Ocean to the Rocky Mountains, was held jointly by Great Britain and the United States from 1818 until 1846, when the international boundary was fixed at the 49th parallel. In 1848 the Oregon Territory was created, including all of present-day Washington and Idaho. The state's current boundaries were established in 1853. Salem is the capital and Portland the largest city.