The Interstate System was first described in a Bureau of Public Roads report to Congress, Toll Roads and Free Roads, in 1939. It was authorized for designation by the Federal-Aid Highway Act of 1944, with the initial designations in 1947 and completed in 1955 under the 40,000-mile limitation imposed by the 1944 Act. President Eisenhower didn’t conceive the Interstate System, but his support led to enactment of the Federal-Aid Highway Act of 1956, which established the program for funding and building it.
President Eisenhower’s support was based largely on civilian needs—support for economic development, improved highway safety, and congestion relief, as well as reduction of motor vehicle-related lawsuits. He understood the military value of the Interstate System, as well as its use in evacuations, but they were only part of the reason for his support.
The primary justifications for the Interstate System were civilian in nature. In the midst of the Cold War, the Department of Defense supported the Interstate System and Congress added the words “and Defense” to its official name in 1956 (“National System of Interstate and Defense Highways”). However, the program was so popular for its civilian benefits that the legislation would have passed even if defense had not been a factor.
No such legislation passed in 1956 or any other year. Nevertheless, this title appears widely throughout the media instead of the correct title: the Federal-Aid Highway Act of 1956.
This myth is widespread on the Internet and in reference sources, but has no basis in law, regulation, design manual—or fact. Airplanes occasionally land on Interstates when no alternative is available in an emergency, not because the Interstates are designed for that purpose.
The Interstate System serves interstate, regional, and intra-State traffic, and was always expected to do so. In fact, many routes, including beltways and spurs, are located entirely in one State and serve primarily intra-State traffic.
Beltways do help traffic avoid cities, but also are intended to serve metropolitan traffic moving from main highway to main highway.
This was not an option in 1955 and 1956 when the congressional debate took place. At the time, transit was provided mainly by private companies. No one in the industry, in State and local governments, or in Congress imagined that the Federal Government would support these companies financially. In fact, the only thing the American Transit Association asked Congress to do was exempt buses from the gas tax. Congress did so.
The numbering plan is helpful in choosing numbers for added routes. However, in an irregularly shaped country, consistency is not possible. The numbers are consistent for the most part, but irregularities have occurred for a number of reasons, such as addition of a route where a consistent number is not available or withdrawal of a route without concurrent renumbering of routes linked to it. These inconsistencies have no effect on motorists who “navigate” based on maps, new GPS technology, personal knowledge or directions, and other means, not the numbering plan.
From an altitude of about 155 miles (250 kilometers), under the best of conditions, the unaided eye of an astronaut can see many built objects on Earth if he or she knows where to look. The Interstate System is not visible as a network, but astronauts using binoculars can see roads, cities, dams, airports, and other objects.