 In Kootenai County, I-90 leaves the river to head over Fourth of July Summit to the lake's north shore and the city of Coeur d'Alene, while the river and trail descends southwest toward Harrison, closer to State Highway 3.The trail is not only a recreational facility, but also a solution to environmental problems left behind by Idaho's mining industry.Silver, lead, and zinc were discovered in the valley around 1884, and a rail line was built to access the mines around 1888.