The first freeway in Los Angeles was a 1930s 'Air Line' route

Nature · Published 20 October 2026 Swipe more like this →

In short: Before the sprawling modern network, a single four-mile stretch of asphalt revolutionized traffic design. Built during the 1930s as a high-speed link to the San Gabriel Valley, this pioneering achievement opened in 1935. It served as the very first freeway in Los Angeles, setting the stage for future infrastructure.

In California, the Santa Monica Freeway serves as the westernmost portion of I-10 and represents the city's inaugural freeway. Built during 1933 to 1935 for $877,000, this 6.4 km (four-mile) stretch is worth roughly $15.7 million today. Originally dubbed the "Air Line route," it was recognized as a major achievement in traffic design when it opened on April 20, 1935.

The evolution of I-10 is a complex layering of historical designations. While it is currently known as the Pearl Harbor Memorial Highway, it was once part of the Atlantic and Pacific Highway. In the 1930s, the route east of Los Angeles was defined by Legislative Routes 26 and 64. By 1932, it began carrying signs for US 60, and by 1936, US 70 was extended across the entire route to Los Angeles. These designations were eventually stripped away during the 1964 and 1972 renumberings, leaving only the I-10 designation.

Today, the freeway remains a vital artery for the National Highway System, essential for the nation's economy and defense. However, its success comes with extreme congestion. The United States identifies the Santa Monica Freeway as one of its ten most crowded locations. To manage this, Caltrans has implemented unique solutions, such as dedicated accident investigation sites separated by fences to prevent "rubbernecking," where drivers slow down to watch crashes, thereby maintaining the flow of through traffic.

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