The Federal-Aid Highway Act of 1956, also known as the National Interstate and Defense Highways Act, was enacted on June 29, 1956, when President Dwight D. Eisenhower signed the bill into law. With an original authorization of $25 billion (equivalent to $ in ) for the construction of of the Interstate Highway System over a 10-year period, it was the largest public works project in American history through that time.
The addition of the term defense in the act's title was because some of the original cost was diverted from defense funds and "because of [the Interstate Highway System']s primary importance to the national defense".
The money for the Interstate Highway and Defense Highways was handled in a Highway Trust Fund that paid for 90 percent of highway construction costs with the states required to pay the remaining 10 percent. It was expected that the money would be generated through new taxes on fuel, automobiles, trucks, and tires. As a matter of practice, the federal portion of the cost of the Interstate Highway System has been paid for by taxes on gasoline and diesel fuel.
History
Some biographers have claimed that Eisenhower's support of the Federal-Aid Highway Act of 1956 can be attributed to his experiences in 1919 as a participant in the U.S. Army's first Transcontinental Motor Convoy across the United States on the historic Lincoln Highway, which was the first road across America. However, there is little evidence in either his private or public utterances from the time (1952–1956) to support this claim. The highly publicized 1919 convoy was intended, in part, to dramatize the need for better main highways and continued federal aid. The convoy left the Ellipse south of the White House in Washington, D.C., on July 7, 1919, and headed for Gettysburg, Pennsylvania. From there, it followed the Lincoln Highway to San Francisco. Bridges cracked and were rebuilt, vehicles became stuck in mud and equipment broke, but the convoy was greeted warmly by communities across the country. The convoy reached San Francisco on September 6, 1919.
The convoy was memorable enough for a young Army officer, 28-year-old Lieutenant Colonel Dwight David Eisenhower, to include a chapter about the trip, titled "Through Darkest America With Truck and Tank", in his book At Ease: Stories I Tell to Friends (Doubleday and Company, Inc., 1967). "The trip had been difficult, tiring and fun", he said. That experience on the Lincoln Highway, plus his observations of the German Autobahn network during World War II, may have convinced him to support construction of the Interstate System when he became president. "The old convoy had started me thinking about good, two-lane highways, but Germany had made me see the wisdom of broader ribbons across the land." His "Grand Plan" for highways, announced in 1954, led to the 1956 legislative breakthrough that created the Highway Trust Fund to accelerate construction of the Interstate System.
Though Eisenhower is sometimes described as having advocated for the highways for the purpose of national defense, scholarship has shown that he said relatively little about national defense when actually advocating for the plan, instead emphasizing highway fatalities and the importance of transportation for the national economy.