Beginning at Chief Mountain Customs on the United States-Canada border in northwest Montana, the Pacific Northwest Trail traverses the high mountains and valleys of Glacier National Park, where it shares mileage with the Continental Divide Trail. Then it enters Flathead National Forest, travels across the Flathead River into Polebridge, Montana, up the Whitefish Divide, into Kootenai National Forest, and through the Ten Lakes Wilderness Study Area on its way to the Idaho state line.