On September 22nd of 1953, the very first four level “stack” interchange (freeway) opened in downtown Los Angeles, California. It was described in the Tuesday Evening Post as “a mad motorist's dream.” Construction had begun back in 1949.
Since July of 2006, the pass is officially known as the Bill Keene Memorial Interchange, so named for a famous weather and traffic reporter. Most people, Bill Keene included, just call it “the stacks.” It is technically referred to as a directional interchange in the American Association of State Highway and Transportation Officials Policy on Geometric Design of Highways and Streets. The Bill Keene Memorial Interchange is the world's first four level stack interchange. It connects U.S. Route 101 (Hollywood Freeway and Santa Ana Freeway) with State Route 110 (Harbor Freeway and Arroyo Seco Parkway). This so called “freeway octopus” features 32 lanes of traffic going in eight directions, all at the same time. It was a landmark moment in civil engineering, however frequently congested and confusing the traffic may have been, and still is. Creepily enough, the center of the “octopus” was placed directly over the former site of the town gallows.
Before the four level design was built, freeways took the form of a cloverleaf, with four circular ramps designed to let motorists merge from road to road without hitting the brakes. However, cloverleafs were considered dangerous, as cars going in both directions had to merge on the same lane. The four level, on the other hand, was designed by stacking long arcs above one another. In this particular area of downtown Los Angeles, the stack made more sense than the cloverleaf, due to the surrounding buildings and terrain.
The Hollywood Harbor Pasadena Santa Ana freeway was the most expensive half mile of highway in the world at that time, costing a whopping (for those days) 5.5 million dollars. That same amount of money today would only pay for about 250 feet of urban freeway.
To build this four level freeway, road builders gutted an entire neighborhood, and four thousand people were put out of their homes. Yet, the four way design has inspired many dozen freeway interchanges across the United States since then, despite that the new four way is every bit as crowded and as risky as the cloverleaf design. Still, the architecture of the stack makes it a virtual symbol of the development of Los Angeles following World War II.
In California alone, there have been no less than eight four level stack interchanges built since the first one was opened back in September of 1953. In the state of Texas, where everything is big, there are quite a few four level stack interchanges, and even a number of five level stack interchanges, also known as high five stack interchanges. The first high fiver was built in Dallas. Also in Dallas, there is a six level stack interchange. Additionally, China is home to many Texas style stack interchanges, with also many five level stacks and even a six level stack.