a large river of North America, which rises in the Rocky mountains near the 54th degree of north latitude, and after receiving the large branches called Lewis river, and Clarke's river, falls into the Pacific ocean in N. Lat. 45° 50' W. Long. 124°. The tide flows up the Columbia 183 miles, and vessels of considerable burden may ascend as far as the first fall, which is 261 miles from the mouth. By means of this river, and the Missouri, whose head branches approach near one another, the Americans have established an inland communication with the Pacific ocean.