On this day in 1968, construction starts on the north tunnel of the Eisenhower/Johnson Memorial Tunnel on Interstate 70 in Colorado, some 60 miles west of Denver. Located at an altitude of more than 11,000 feet, the project was an engineering marvel and became the world's highest vehicular tunnel when it was completed in 1979. Four months after opening, one million vehicles had passed through the tunnel; today, some 10 million vehicles drive through it each year.
The north tunnel (or bore) was finished on March 8, 1973 and named for America's 34th president, who was in office from 1953 to 1961. Construction on the south tunnel began on August 18, 1975, and was finished on December 21, 1979. The south tunnel was named for Edwin C. Johnson, a Colorado governor and U.S. senator who was a big supporter of an interstate highway system across his state. (Interstate 70 stretches more than 2,100 miles from Interstate 15 near Cove Fort, Utah, to Baltimore, Maryland. It was America's first interstate highway project. Construction began in 1956 and ended in 1992 in Glenwood Canyon, located near the city of Glenwood Springs in western Colorado.)
The north tunnel cost $117 million to construct and at the height of the building process, some 1,140 people worked three shifts, 24 hours a day, six days a week. The south tunnel cost $145 million and employed 800 workers, approximately 500 of whom were involved in drilling operations.
The Eisenhower/Johnson Tunnel cuts through the Continental Divide at an average elevation of 11,112 feet. (Driving conditions around the tunnel can be challenging during the months between November and April: The surrounding area receives an average of 26 feet of snow during those months.) The north tunnel, which handles westbound traffic, is 1.693 miles long, while the south tunnel (eastbound traffic) is 1.697 miles. Illuminating those tunnels is no small task--each has approximately 2,000 light fixtures using 8-foot bulbs.
The Eisenhower/Johnson Tunnel is an impressive accomplishment, but it's small potatoes compared to some others. The 15.2 mile-long Laerdal Tunnel in Norway is the world's longest road tunnel. One of the busiest vehicular tunnels in America is the Lincoln Tunnel, which was built under the Hudson River to connect New Jersey and Midtown Manhattan in New York City. That tunnel's center tube opened in 1937, while its north tube opened in 1945 and its south tube in 1957. In 2008, some 41,874,000 vehicles passed through the Lincoln Tunnel.