The Federal Aid Highway Act of 1956, also known as the National Interstate and Defense Highways Act, Pub.L. 84–627 was enacted on June 29, 1956, when President Dwight D. Eisenhower signed the bill into law. With an original authorization of $25 billion for the construction of 41,000 miles (66,000 km) 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 for two reasons: First, some of the original cost was diverted from defense funds. Secondly, most U.S. Air Force bases have a direct link to the system. One of the stated purposes was to provide access in order to defend the United States during a conventional or nuclear war with the Soviet Union and its communist allies. All of these links were in the original plans, although some, such as Wright Patterson AFB were not connected up in the 1950s, but only somewhat later.The money for the Interstate Highway and Defense Highways was handled in a Highway Trust Fund that paid for 90% 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.