The first modern freeway in California, and the Western United States, opened to the public on this day in 1940. Connecting downtown Los Angeles and Pasadena along the season Arroyo Seco River, the Arroyo Seco Parkway motored the US into a new era of transportation. At just 8.162 miles, the roadway is now part of State Route 10. It has since been designated a State Scenic Highway, National Civil Engineering Landmark, and National Scenic Byway.
The freeway is home to the first stack interchange in the world, known as the Bill Keene Memorial Interchange. The Four Level Interchange first opened in1949 and by 1953 the city deemed it fully operational. The crisscrossing roads connected US Route 101 and SR 110.