Kettle River Range Mountains, which in turn form part of the Columbia Mountains. The range runs north to south, bordered on the east by the Kettle River and the Columbia River, and on the west by the Kettle River, the Curlew Valley and the San Poil River. The mountainous region begins immediately north of the Canada–US border, at Grand Forks, British Columbia, extending 110 miles (177 km) south to the bend of the Columbia River and Lake Roosevelt, formed by Grand Coulee Dam, where it terminates. The Okanogan Highlands are adjacent to the range on the west, and the Selkirk Mountains are adjacent
Grand Coulee wide as Niagara Falls and three times as high. Steamboat Rock high and a in area, now stands as an isolated rise, but for a time it created two cataract. When the falls passed north of Steamboat Rock, it found a granite base beneath the basal flows. Granite lacks the close vertical joints of basalt, was resisted the erosion from the cataract's plunge. It remains as hills on the broad floor of the Coulee. Some gravel-bar deposits are visible along the Route 155. They provide evidence of eddies in the lee of rock shoulders. Dry Falls is at the head