"When Clifford M. Holland talks tunnels, his listener is in danger of being convinced that tunnels are the only refuge for mankind; by the time he has finished his hearer sees in a tunnel all the allurement which a mole finds in a nicely constructed burrow. Because Mr. Holland does know tunnels, and he does build them safely." - Brooklyn Daily Eagle, February 29, 1920.

1906 - A joint New York and New Jersey commission is created to investigate the feasibility of building a bridge across the Hudson. The bridge is rejected in favor of a tunnel in 1913 because a bridge high enough to clear harbor shipping required the purchase of a prohibitively costly amount of access land. Moreover, tunnels are felt to be less directly affected by weather.

1919 - Clifford Milburn Holland takes office as the Chief Engineer on the Hudson River Vehicular Tunnel project. A thirty-six-year-old father of four from Brooklyn, Holland dies suddenly in 1927, of apparent exhaustion, on the eve of the day workers from the New York and New Jersey sides are to meet in the middle (a process called "holing through"). The tunnel to be named for Holland was the world's first long underwater mechanically ventilated vehicular tunnel.

1920 - Construction on the tunnel begins October 12. The biggest challenge is ventilation. There is no precedent for building such a tunnel and ensuring safe ventilation. It is feared that dangerous accumulations of poisonous automobile exhaust fumes will make travel through the tunnel impossible. Holland tunnel engineers design an automatic ventilation system that produces purer air under the Hudson than was to be found above. Fresh air is supplied to the tunnel every 90 seconds. The air is moved by 42 blowing and 42 exhaust fans of 6,000 total horsepower arranged in four ventilation buildings. The solution to the ventilation problem is devised by Ole Singstad, who succeeds Milton H. Freeman as Chief Engineer when Freeman dies five months after taking Holland's place.

1927 - The tunnel opens after seven years of construction, during which only thirteen "sandhogs" (as the construction workers were called) die. The greatest danger facing the workers is the bends. Construction is carried out under air pressure, which has to balance river pressure. Workers have to pass through decompression chambers, much as divers do coming up from deep water. None of the worker fatalities are from the bends, however. The toll in 1927 is fifty cents, and the trip takes only eight minutes. The tunnel when it opens is the longest underwater tunnel in the world, with its north tube 8,558 feet long and its south tube 8,371 feet long. On its first day of operation, 51,694 vehicles pass through. The total cost of the tunnel is $48 million. Today, it would cost approximately $1.4 billion.

1931 - Control and operation of the Holland Tunnel is vested in the Port Authority.

1949 - On May 13, a chemical truck loaded with 80 drums of carbon disulfide burns on the New Jersey side of the south tube. The wall surfaces and ceiling slabs are demolished for a distance of 600 feet. Amazingly, no one dies in the explosion and fire, although there are 66 injuries. The fire causes an estimated $600,000 in damage to the structure-and as a result of this accident, strict standards are established for the transporting of explosives.

1984 - Considered an outstanding engineering achievement, the Holland Tunnel was given special status as a National Civil Engineering Landmark by the American Society of Civil Engineers.

1992 - A complete renovation of the entire toll plaza and administration building is completed. Through the end of the following year, the Port Authority's investment in the tunnel totals more than $272.5 million. The tunnel is operated around the clock by a staff of some 300 employees, including operations staff, police, toll collectors, and maintenance workers. Since its completion, an estimated 1.3 billion vehicles has used this landmark