According to Fred Beckey there are differences of opinion about the names and locations of the subranges of the northern Cascades, especially between Canadian and American geographers. Nevertheless, early geologists and topographers had a fundamental agreement about the location and names of the subranges. The Skagit Range was seen as the mountainous area from the Skagit River northwest to the Fraser River. More recent Canadian maps show the Skagit Range as bounded to the west by the Sumallo-Nicolum valley and extending north along the east side of the Coquihalla River.