In 1807, the Pennsylvania legislature commissioned a road across the wilderness of northern Pennsylvania to open east-west travel, and nine years later laborers completed it, though some sections remained rough packhorse trail, including in Potter County, which had just 29 residents in 1810. Often impassable with deep mud and heavy snows, and unpaved until the late 1920s, the route still served as an artery for community commerce and westward migration and linked the county seats of Pennsylvania's Northern Tier counties. In all but a few stretches, the present-day Route 6 Heritage Corridor follows this original east-west road. From Warren to Mansfield, Route 6 passes through the northern Pennsylvania Wilds, historic communities, and a landscape of deep forests, rushing streams, and scenic vistas. Historical society museums preserve the region's past in Warren, Smethport, Coudersport, and Wellsboro, and historic districts line the route from Wellsboro to Warren. Kinzua Bridge, just north of Route 6 at Mount Jewett, stretched 2,053 feet across the Kinzua Valley, 301 feet above the creek, and though partly destroyed in 2003 when a tornado tore down many of its support towers, the viaduct remains an engineering wonder. Near Warren, Kinzua Dam, built on the Allegheny River in 1964 to control flooding, creates the 12,000-acre Allegheny Reservoir.