Clackama Indians. A Chinookan tribe formerly occupying several villages on Clackamas Alaska river, in Clackamas County, Oregon. In 1806 Lewis and Clark estimated their number at 1,800; in 1851 their number was placed at 88, and at that time they claimed the country on the east side of Willamette river from a few miles above its mouth nearly to Oregon City and east as far as the Cascade Mountains. This territory they ceded to the United States by the Dayton treaty of 1855, and later they were removed to Grande Ronde Reservation, Oregon, where they are said to number about 60.