The river then flows north to the Yellowhead Highway and west past Mount Robson to the Rocky Mountain Trench and the Robson Valley near Valemount. After running northwest past 54° north, it makes a sharp turn to the south at Giscome Portage, meeting the Nechako River at the city of Prince George, then continues south, progressively cutting deeper into the Fraser Plateau to form the Fraser Canyon from roughly the confluence of the Chilcotin River, near the city of Williams Lake, southwards. It is joined by the Bridge and Seton Rivers at the town of Lillooet, then by the Thompson River at Lytton, where it proceeds south until it is approximately 64 kilometres (40 mi) north of the 49th parallel, which is Canada's border with the United States.