Interstate Highway System

The Dwight D. Eisenhower National System of Interstate and Defense Highways is a massive network of controlled-access highways. It forms a vital part of the National Highway System in the United States. These highways connect the contiguous United States and include routes in Alaska, Hawaii, and Puerto Rico.

The system matters because it allows for the rapid movement of people and goods across vast distances. It also serves a critical role in national defense by ensuring the military can move quickly between locations.

To ensure safety and speed, all Interstates must follow strict federal standards. They are designed as freeways, which means they have controlled access to traffic. Drivers enter and exit via specific ramps rather than at intersections.

These roads must have at least four lanes and include breakdown lanes for stopped vehicles. To prevent head-on collisions, the system requires physical barriers or median strips between lanes of oncoming traffic. Most importantly, Interstates avoid at-grade intersections and traffic lights entirely.

The system uses a specific numbering scheme to help travelers navigate. Primary Interstates are assigned one- or two-digit numbers. Shorter routes that branch off from these main roads are given three-digit numbers.

In this auxiliary system, the last two digits of the three-digit number match the parent route. This allows drivers to understand how different roads connect to the larger network.

The journey toward this network began long before the 1950s. In 1916, the Federal Aid Road Act provided matching funds to states for road improvements. Later, in 1921, the Federal Aid Highway Act aimed to create a national road grid.

In 1922, General John J. Pershing submitted the "Pershing Map," which outlined a network of interconnected primary highways for national defense. Even President Franklin D. Roosevelt contributed to the planning. In 1938, he provided a hand-drawn map showing eight superhighway corridors for study.

President Dwight D. Eisenhower became the system's greatest champion. His interest was sparked by a 1919 military convoy trip. As a young officer, he traveled across the country in a Motor Transport Corps convoy.

He experienced firsthand the difficulty of driving on roads filled with dust, ruts, and holes. He also studied the German Autobahn system while serving in Europe during World War II. This experience helped him realize the importance of a modern, national highway network. In 1956, he signed the Federal-Aid Highway Act, which provided the necessary funding and structure.

Building this system was a monumental task with significant costs and social impacts. The construction of the original system cost approximately $114 billion.

While the federal government pays 90 percent of construction costs, the individual states own the highways within their borders. However, the process was often difficult for local communities. In dense urban areas, new routes were sometimes built through well-established neighborhoods as part of "urban renewal." This displaced approximately one million people during the two decades following the 1956 Act. Such actions led to many "freeway revolts," causing some planned routes to be abandoned or moved.

Despite these challenges, the system reached major milestones. The construction of the original system was proclaimed complete in 1992.

Significant achievements include the completion of Interstate 5, which connects Canada to Mexico, in 1979. In 1986, Interstate 80 became the world's first continuous freeway to span from the Atlantic to the Pacific Ocean. Today, the system remains active. It is partially financed through the Highway Trust Fund, which uses federal gasoline taxes. The network continues to grow as new routes are planned and built to meet the needs of the country.