From the Columbia River to the Siskiyou Mountains, Highway 99 traverses 300 miles of western Oregon. Big cities and small towns, the level Willamette Valley and steep hills, rich agricultural lands and tall evergreen forests, and rushing rivers all lie along its path. Arising from an early network of emigrant trails, stagecoach routes, and farm-to-market roads, the highway had developed into Oregon's major transportation corridor by the end of the...