It seems that it has been around forever, and most of us use it without giving it a second thought. It is 46,000 miles long and though it comprises only 1% of the nation’s roads, it accounts for 41% of the total truck miles traveled each year. It is the Interstate Highway system and it turns 50 years old this year.

Technically known as the Dwight D. Eisenhower National System of Interstate and Defense Highways, the Interstate as it is commonly called, is a marvel of modern engineering with statistics rivaling those of other great manmade “wonders of the world” such as the Great Wall of China and the Pyramids.

Some of the statistics regarding the Interstate System are truly astounding. For example – Americans travel nearly 700 billion miles a year on the Interstate System. There are 55,000 bridges, almost 15,000 interchanges 1,214 rest areas and 82 tunnels within the system. Some 2.4 billion man-hours of construction time have been spent on building and maintaining the system. Laid out straight the Interstate System would almost circle the Earth twice.

Though largely taken for granted now, the Interstate Highway System was a project that literally took decades to go from the drawing boards to the first mile of roadway. In large part construction of the Interstate System came about because of two experiences, separated by a quarter century, in the life of President Dwight David Eisenhower.

In 1919 Lieutenant Colonel Dwight D. Eisenhower volunteered to participate in the first U.S. Army transcontinental motor convoy from Washington D.C. to San Francisco, CA. The purpose of the convoy was to determine if it was possible for a military convoy consisting of 300 men and several dozen trucks, motorcycles and tractors to cross the continent. Such a crossing was by no means assured since the “road system” in most of the country was little more than rutted dirt roads and mountain passes that were frequently impassable. Breakdowns and accidents plagued the convoy during the 3251 mile trip. It took 62 days to complete the journey at a speed that averaged out to a breath taking 6 miles per hour.

That experience stayed with Eisenhower and its memory was renewed when, 26 years later, Eisenhower led the occupation forces in Germany and marveled at the modern and efficient German national highway system, the autobahn. Said Eisenhower, "after seeing the autobahns of modern Germany and knowing the asset those highways were to the Germans, I decided, as President, to put an emphasis on this kind of road building. ... The old [1919] convoy had started me thinking about good, two-lane highways, but Germany had made me see the wisdom of broader ribbons across the land."

As noted earlier the technical name for the Interstate System is the Dwight D. Eisenhower National System of Interstate and Defense Highways. The “Defense” element is important, since construction of the system began in the midst of the cold war and, like the autobahn, one of the original requirements for the Interstate System was that it be designed to be able to run military equipment from coast to coast on flatbed trailers at sustained speeds of 75 miles per hour.

On June 29, 1956 President Eisenhower signed the Federal Aid Highway Act which provided funding and began development and construction of the Interstate System. Its 50th anniversary is being celebrated by the U.S. Department of Transportation and by the American Association of State Highway and Transportation Officials, AASHTO.

On June 16th AASHTO will kick off a national convoy that will duplicate the 1919 transcontinental Army convoy, only this time the convoy will start in San Francisco and end in Washington D.C. on June 29th.

• East-West Routes end in an even number (with a small number of exceptions), North-South Routes end in an odd number.
• On East-West Routes the highest numbered route is the farthest North, with the numbers getting smaller the farther South you go.
• On North-South Routes the highest numbered route is the farthest East, with the numbers getting smaller the farther West you go.
• I-90 is the longest Interstate Route. It is 3,020.54 miles from Seattle Washington to Boston, Massachusetts.
• I-73 is the shortest Interstate Route. It is in North Carolina and is only 12.27 miles long.
• If a city bypass has an even number it loops back to the same Interstate. For example I-220 ends back up on I-20.
• If a city bypass has an odd number, e.g., I-520, it is called a spur and does not end up back on the Interstate.
• Interstate Highways are the safest roads in America, with a fatality rate of 0.8 per 100 million miles, compared to 1.46 per million miles for all other roads. – FHWA 2004 statistics.