The landmark plaque designating the Hudson & Manhattan Railroad Tunnel as a National Historic Civil Engineering Landmark was unveiled at the PATH Hoboken Terminal on October 31, 1978.

The tunnel under the Hudson River is part of the interstate commuter railroad familiarly known as the PATH system. Construction of the tunnel stretched out over a period of more than three decades beginning in 1874 with the Hudson Tunnel Railroad Company when the use of compressed air in sub-aqueous tunneling was introduced. Difficulties in advancing the tunnels delayed progress and in 1882 work was halted when funds ran out. Work was resumed in 1889 this time using the shield method of tunneling that had proven successful in the construction of the London Subway. However, work came to a halt in 1892 again because of financial difficulties.

In 1902 a new company, the Hudson and Manhattan Railroad, was formed to undertake the completion of the project. Assured of adequate financing, the work was resumed and, in spite of numerous obstacles to the driving of the shields, the tunnel was brought to a successful completion. In 1908 the first train passed under the Hudson River and the railroad began its operation. All of the work was substantially completed by 1910, except for the route extensions in Manhattan and New Jersey which were completed in 1912.

The first train through the Hudson and Manhattan Railroad Company Tunnel (McAdoo system) carried passengers between Hoboken, New Jersey and 19th Street in Manhattan on February 26, 1908.

In its early years the railroad was well patronized and profitable but during the depression of the 1930's, ridership began to drop off drastically. In the 1950's the Hudson and Manhattan Railroad Company was in bankruptcy and the condition of the railroad had deteriorated seriously from lack of maintenance. To avoid total abandonment the Port Authority of New York & New Jersey took over the railroad in 1962, made extensive repairs and improvements, including new rolling stock, and began operating the PATH system as we know today.

The Hudson River Tunnel in its long period of construction served as a proving ground for new underwater tunneling methods and as a training school for engineers who later became leaders in shield driven tunnel construction.

The unveiling of two bronze plaques designating the Hudson and Manhattan Railroad Tunnel as a Historic Civil Engineering Landmark occurred on October 31, 1978. One plaque was placed in the Hoboken station and another plaque was placed in the World Trade Center. Both ceremonies were well attended and addressed by Chairman Alan Sagner of the Port Authority and Peter Goldmark, the Authority's executive director. Officials representing the governors of both states and the Mayors of New York City and Hoboken addressed the audience.

Following the ceremony at the Hoboken Terminal, attendees rode a special train to New York City and unveiled a second plaque at the World Trade Center PATH station.

Walter E. Blessey, president of the American Society of Civil Engineers, unveiled the plaques and presented them to the Port Authority in a formal address in which he addressed the Society's national historic civil engineering landmarks program.

Members of the family of William G. McAdoo attended the ceremony and his grandson, Brice McAdoo Clagett, spoke about how his grandfather headed the organization that finally completed the railroad project in 1910 after many years of starts and abandonments beginning in 1874.

At the close of the ceremony in the Hoboken terminal those attending boarded a special train for a trip through the tunnel to New York. Approaching the World Trade Center, the train was halted in the tunnel and the passengers transferred to flat cars attached to the train for an inspection of the tunnel and a description of the structure by John F. Hoban, the Port Authority's director of rail transportation. The train then continued to the World Trade Center for the ceremony unveiling the plaque in New York.