Columbia Or Oregon (River), a river of N. W. America, rising in Otter lake on the W. slope of the Rocky mountains, in British Columbia, in lat. 50° 30' N, lon. 116° W. It flows N. W. to lat. 52° 10', where it receives the Canoe, which rises in about lat. 52° 40', then turns W. and S., and flows in a general S. direction to the boundary of the United States, whence, entering Washington territory, its course lies through the great plain between the Cascade and Rocky mountains to the 46th parallel. Here turning somewhat abruptly, it flows in a general W. direction, forming the boundary between Washington territory and Oregon, and falls into the Pacific in about lat. 46° 15', lon. 124° W. There is a remarkable bend in lat. 47° 55', lon. 118° 10', where the river turns nearly due W., and continues in that direction about 120 m. to the mouth of the Okina-kane. It then flows S. W. about 50 m., when it turns S. E., and flows in that direction about 165 m. to the 46th parallel. Throughout its entire length the Columbia is very rapid, often passing through mountain gorges and broken by many cataracts. The tide sets up 165 m. to the Cascades, which are a series of rapids caused by the passage of the stream through the Cascade range.

At a distance of about 30 m. from the ocean the river expands into a kind of bay from 3 to 7 m. wide, which forms its mouth. At low tide there is about 20 ft. of water over the flats at the entrance to this bay, while the depth of the channel is 24 ft. Ocean steamers can ascend to Vancouver, 115 m. above the mouth, and steamers of 200 or 300 tons to the Cascades, around which there is a railroad 6 m. long. The Dalles, 40 m. further, again obstruct navigation. Here the river bends like a horseshoe to the south, and flows with a rapid current through a basaltic trough with walls 20 ft. high and 200 yards apart. Other falls, with stretches of navigable water between, are Priest' rapids, 179 m. above the Dalles; Buckland rapids, 66 m. further; and Kettle falls, 274 m. above. The last is a perpendicular fall of 15 ft. At high water (from the middle of May to the middle of July) steamers could probably ascend from the Dalles to Kettle falls. Above Kettle falls the river is again navigable about 50 m. to falls just N. of the 49th parallel. Above the head of Upper Arrow lake, lat. 50° 30', there is no navigable water. At Vancouver the Columbia is a mile wide. Its total length is over 1,200 m.

The rise at Vancouver during high water is 19 or 20 ft., and so great is the force of the current as to overcome the effect of the tide, and render the water drinkable even on the bar. The principal E. branches are the Kootenay (also called McGillivray or Flat Bow), which joins the Columbia in British territory about 20 m. N. of the boundary; Clarke's or Flathead river; the Spokane; and Lewis fork (also called the Saptin or Snake river), which is the great southern tributary, and rises in the Rocky mountains in W. "Wyoming, about lat. 44°, lon. 110° 30'. The tributaries from the west are smaller; the chief are the Nehoialpitkwu, Okinakane, and Yakama. Below the great bend several streams empty into the Columbia from the north, the largest of which is the Cowlitz; from the south it receives the Umatilla, John Day's river, the Des Chutes, and the Willamette. - Columbia river was discovered in 1792 by Capt. Robert Gray, who entered it May 11 of that year, in the Columbia Rediviva, of Boston, Mass. It was from this vessel that the river received its name.

The first exploration of the Columbia was made in 1804-'5, by Captains Lewis and Clarke, under the direction of the war department.