History of Interstates and U.S. Highways in Arizona

Arizona's Interstates and U.S. Highway system is integral to the state's transportation and commerce, with a history that began in the 1920s with the creation of U.S. Routes 60, 70, and 80. These early highways connected the state to California, New Mexico, and other parts of the Southwest, providing vital trade routes. With the establishment of the Interstate Highway System in the 1950s, Arizona saw the construction of I-10, I-17, and I-40, which transformed the state's infrastructure and boosted its economy.

Today, Arizona's highways handle heavy traffic, particularly in urban areas like Phoenix and Tucson, where Interstates like I-10 can see traffic volumes of over 200,000 vehicles per day. Arizona's highways are also essential for moving goods, particularly along the I-10 corridor, which connects the state to major ports in California and Texas. The state's economy relies heavily on these highways for the transportation of goods, including agricultural products, electronics, and other manufactured goods.

Arizona is continually expanding its Interstate system to accommodate its growing population. Major projects include the widening of I-10 in Phoenix and Tucson, as well as the construction of the Loop 202 South Mountain Freeway in Phoenix, which will improve traffic flow in the metro area. Future projects include the proposed I-11, which would run from the Mexico border to Las Vegas, providing a critical new north-south route.

Why all the 1926 dates? The year 1926 was significant for the U.S. highway system because it marked the official establishment of the U.S. Numbered Highway System, also known as the U.S. Highway System. This system was created by the American Association of State Highway Officials (AASHO), now known as the American Association of State Highway and Transportation Officials (AASHTO), in cooperation with the federal government. Here’s why 1926 was pivotal:

1 Standardization of Routes: Prior to 1926, roads in the United States were a patchwork of local and state routes, often inconsistently marked and poorly maintained. The U.S. Highway System brought about a standardized network of numbered routes, designed to provide uniformity across state lines, making travel more predictable and navigable for drivers.

2 National Connectivity: The new system connected rural and urban areas across the country, linking small towns and cities with major economic hubs. This was essential for improving the transportation of goods and services, helping to bolster the national economy.

3 Designation of Major Routes: Iconic highways such as U.S. 1 (from Maine to Florida) and U.S. 66 (from Chicago to Los Angeles, later known as "Route 66") were part of this network. These routes became crucial arteries for cross-country travel, commerce, and later, American culture.

4 Foundation for the Interstate System: The 1926 U.S. Highway System laid the groundwork for the more advanced Interstate Highway System, which was developed decades later in the 1950s under President Eisenhower. Many U.S. Highways continue to serve alongside interstates, and some of the old U.S. highways are still in use today.

The year 1926 thus represents the beginning of a modern, structured approach to road travel in the United States, which revolutionized transportation and mobility across the country.

Busiest and Longest Federal Interstates and U.S. Highways in Arizona