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Cumberland Gap Tunnel

Cumberland Gap Tunnel

The Cumberland Gap Tunnel carries four lanes of US Route 25E under Cumberland Mountain between Kentucky and Tennessee.


The Wilderness Road served as the principal route from Virginia and other east coast colonies to lands west of the Alleghenies and was formed from several different earlier primitive roadways. One of those paths was Daniel Boone’s Boone Trace which snaked through Cumberland Gap and the Bluegrass region which was completed in 1775. Between 1775 and 1810, as many as 300,000 settlers had traveled along the Wilderness Road.

A more modern Wilderness Road was built through Cumberland Gap in 1916 and designated US Route 25E in 1926. 1 8 By the 1950s, heavy traffic and high accident rates on the 2.3 mile mountain crossing between Middlesboro, Kentucky and Cumberland Gap, Tennessee gave the road a more dubious nickname: Massacre Mountain. 5 11 The first discussion of a tunnel under Cumberland Gap was discussed as early as 1956 by the National Park Service, and studies were conducted over the following decades that confirmed the recommendation of a tunnel to improve the US Route 25E corridor without damaging the scenic and historic significance of the area.

From Proposal to Construction

The earliest work to build the Cumberland Gap Tunnel began in earnest in 1979 when geologists examined exposed rock on the surface of the mountain and identified the different rock types. 1 A 2,000-foot small-diameter horizontal core hole was then drilled to provide even more geologic detail. A 4,100-foot pilot tunnel 10-feet high and 10-feet long was excavated that revealed many characteristics of the mountain that would later pose challenges in excavatation. Thick clay infillings, limestone formations, and caves, along with underground streams and a lake were encountered. Numerous underground streams were a major challenge as well. Congress appropriated some money for the construction of a tunnel but the funding was later removed by the President Carter administration. 11

The battle to improve the Cumberland Gap crossing dragged on for the next two decades, eventually leading to an all-out funding freeze by the President Reagan administration in 1984. 11 At the urging by U.S. Congressman Hal Rogers, the Cumberland Gap Tunnel project became part of a highway budget that did not require annual reauthorization, giving it a stable financial footing. Another boost to the project was the commitment of at least $2 million by the states of Kentucky and Tennessee to later operate and maintain the finished tunnels, which received Reagan’s approval.

In 1985, engineers drilled a second pilot tunnel to better understand the inner geology of Cumberland Mountain. 11

By the early 1990s, US Route 25E over Cumberland Gap was carrying twice as much traffic as it was safely designed to handle and had an accident rate six times higher than on similar highways. 11 The proposed 4,600-foot long Cumberland Gap Tunnel, once projected to cost $156 million in 1985, 8 9 had ballooned to $250 million to $270 million and it was thought that it would take 2½ to three years to finish excavation work. 11

Construction began with the blasting of the northbound tunnel on June 21, 1991, 3 followed by excavation of the northbound and southbound tubes from the Kentucky and Tennessee sides of the mountain with work encountering a few obstacles. While constructing a drainage system for the huge caverns that lay just outside of the tunnel walls, workers discovered that one of the caves had become clogged with rock. The blockage forced water to blow out a small chunk of the northbound tunnel wall. 11 On July 9, 1992, after 1,947 days of digging, the tunnel boring process was complete. 3

The new tunnel was bored through 4,600 feet of solid rock, 11 each with a height of 30 feet with cross passages located every 300 feet to provide pedestrian access between the tubes. 2 Each crossover was equipped with fire extinguishers and phones for emergency use. Separate water storage tanks were located on-site for use in the event of a fire. 1 2 To keep the tunnel dry, 32 jet-powdered fans were installed every 600 feet keep air circulating inside. 1 2 4

Included in the construction of the tunnel were five miles of four-lane approaches, two interchanges, seven roadway bridges, a 200-foot railroad bridge, two pedestrian bridges for hiking trails, three parking areas, and the repair of an abandoned railroad tunnel under the former US Route 25E alignment so that it could host electrical, telephone, cable and water lines under the new US Routes 25E and 58 interchange. 1 2 The use of sandstone masonry, Corten weathering steel, concrete blended with earth tone elements, and the planting of native trees helped blend the new highway and tunnel with Cumberland Gap.

The Cumberland Gap Tunnel dedication ceremony involving officials from Kentucky, Tennessee, Virginia, and the National Park Service was held on October 18, 1996. 11

Seventeen years in the making, the Cumberland Gap tunnel project has spurred highway expansion in three states, hopes for tourism in small communities near the Gap, and dreams of restoring the wilderness trail that Daniel Boone blazed in the 1700s. The tunnel is “the most significant thing that has happened there since Daniel Boone began to bring settlers through the Gap.” 9
– U.S. Rep. Hal Rogers

The former US Route 25E alignment through Cumberland Gap was removed in 2002 and the land recontoured as to resemble the original wagon trail at the cost of $5 million. 10 11 The National Park Service utilized tons of rock excavated from the tunnel to reshape the topography of the trail as to what it resembled in the 1700s.



  • State: Kentucky, Tennessee
  • Route: US Route 25E
  • Type: Tunnel
  • Status: Active - Automobile
  • Total Length: 4,600 feet
  • Spans:
  • Roadway Width: 36 feet (×2)
  • Height: 30 feet (×2)


  1. “Bridging the Gap.” News-Sentinel (Knoxville) 14 Oct. 1996. Aug. 2004: A6.
  2. “The Cumberland Gap Tunnel.” Eastern Federal Lands Highway Division. Federal Highway Administration. 21 June 2005 Article.
  3. “The Cumberland Gap Tunnel.” National Park Service 10 May 1999. 21 June 2005 Article.
  4. “Cumberland Gap Tunnel ITS Project Home.” Kentucky Transportation Center. 20 June 2005 Article.
  5. Droz, Robert V. “Old US 25E: Crossing the Cumberland Gap.” U.S. Highways 20 June 2002. 20 June 2005 Article.
  6. Elkins, H.B. “Cumberland Gap Tunnel Opening Ceremony.” Online posting. 21 Oct. 1996. 19 June 2005 Post.
  7. * “Parkway System & Cumberland Gap Tunnel Project Selected Kentucky’s Top Transportation Infrastructure Projects of 20th Century.” 6 Dec. 2002. 19 June 2005 Article.
  8. “Touch of the unknown makes mountain tunnel risky.” Miami Herald 7 Mar. 1986. 20 June 2005 Post.
  9. “A tunnel to the future.” Herald-Leader 13 Oct. 1996. August 2004: A1.
  10. “Will underground passageway boost tourism in the area? Officials say yes.” News-Sentinel (Knoxville) 14 Oct. 1996. August 2004: A6.
  11. Dias, Monica. “Cutting through the Gap.” Kentucky Post 13 July 1996. 28 Nov. 2007: 1K.

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