Twenty-six tunnels carry the parkway through mountain spurs and ridges. Twenty-five of these are in North Carolina; the Bluff Mountain Tunnel at milepost 53.1 is the only tunnel located in Virginia. The tunnels were often constructed to reduce excessive landscape scaring that open cuts would entail, though in several cases they enabled the parkway to cross through ridges in the interest of maintaining the most desirable route location. Most of the tunnels were constructed with drilling "Jumbos", truck-mounted platforms equipped with water-cooled drills. The drills would bore into the substrata, after which the Jumbo would be removed and blasting stone masonry portals on most parkway tunnels were generally not part of the original construction, but were added later, mostly in the 1950s and 1960s.
Text excerpted from "Highways in Harmony" publication produced by Historic American Engineering Record (HAER), in cooperation with the National Park Foundation.