The Paw Paw Tunnel is one of the major features of the canal, built as a bypass to some very difficult terrain along the Potomac River in Paw Paw Bends. Here the river makes a series of gargantuan loops, the tunnel route cutting across one large double loop takes 1 m. where river takes 6. While tunnel route involved cutting thru 3118' of solid rock, the MD shore of river route contains some impressive cliffs coming right down to the river To have followed river would have required either crossing to W.Va. shore and back hacking out canal along those cliffs or damming river at lower end of bend to form a slackwater and cutting a towpath along cliffs or putting towpath on W.Va. side. The alternatives were thoroughly debated within the canal co. and, due largely to enthusiastic advocacy of newly-appointed engineer, Charles B. Fisk, the tunnel plan won out. Even when work was well advanced the board of directors seriously contemplated abandonment of the partially-completed tunnel in favor of a dam. Decision was made to proceed with the tunnel in Feb. 1836, with completion date set for July 1838. In actual fact, tunnel was not completed until 1850, though holed thru in 1840. Two other men responsible for building of the tunnel were Fisk's assistant, Elwood Morris and the contractor, Lee Montgomery.
Somehow despite failing finances and violent unrest, work continued thru 1840 and 1841, but in 1842 the canal co. collapsed and work on the entire canal ceased. The canal was completed and operating up to Dam No. 6 (134.1), about 20 m. below the tunnel. In addition, much of the stretch above the tunnel to Cumberland had been finished. Montgomery, who now disappears in a maze of lawsuits, his personal fortune sunk in abortive attempt to finish the tunnel, had actually driven it thru, but a great deal of work remained. North of the tunnel the deep cut, plagued by slide was not fully cleared, and of course the canal in this cut had to be completed. The tunnel itself was not yet completed and still had to have brick lining installed. Morris by this time found Montgomery and his patented machine made poor brick. Fortunately for the canal, state and federal interests were involved and ways were found to raise enough money to resume work under a new contractor in 1847. The tunnel and canal were finished and opened to traffic in 1850.
At the tunnel entrance the tunnel lining is dressed stone and from then on to 26' below south portal it is a brick four courses thick except under the vertical shafts where it is six. Tunnel has 12' radius set on 11' vertical walls. Towpath runs on a ledge about 4' wide and equipped with a stout railing a little better than waist high. Top rail is a square stout beam, in many places showing deep ruts burned into it by tow ropes of mule drawn barges. There are wooden railings or bumpers on both inner sides of tunnel to keep barges from scraping brick walls. Height of tunnel 24 1/2'; 17 1/2' above water. Volume of rock cut out in tunnel 82,000 cubic yds. Greatest depth 44'. Canal 17' wide.
"Weep" holes are occasionally placed at spring line of arch to prevent seepage of water from building up and coming directly thru brick, an admirable precaution, but one sees that it does not seem entirely effective as a great many patches are visible in the lining. Park Service did a thorough renovation of interior of tunnel in 1966; it now remains in excellent shape. The two sets of vertical shafts from surface of hill overhead are fairly easy to locate by extensive seepage of water coming thru brick lining from them.