Next year will be the 70th anniversary of the completion/opening of the Pasadena Freeway, the oldest freeway on the west coast, which runs from downtown Los Angeles to Pasadena. It was originally called the Arroyo Seco Parkway. When it opened, it became the new alignment for the famed US Route 66. In 1954 it was renamed the Pasadena Freeway. I think it's still officially called the Pasadena Freeway but some years ago the State of California officially declared it a historic highway, so there are a few signs that call it the Historic Arroyo Seco Parkway. Its Route 66 designation ended in 1964 when it was re-signed state route 11. Since 1981, it's been California State Route 110.
Here are some photos of its early years, all from the USC Archive.
1941
1942. Then, as now, on most onramps, you have to make a complete stop before entering the freeway. And on many offramps, the driver is forced to slow down abruptly to 5 miles per hour. On/offramps are extremely short by modern freeway standards, and there are virtually no acceleration/deceleration lanes. Freeways built after this one benefited from these design flaws; obviously, highway engineers realized you need longer ramps and space to accelerate/decelerate.
DO NOT ENTER signs, 1942
New signs, 1951. I guess this freeway originally had those smaller signs you see. The larger, taller signs are obviously better for motorists, and were just recently installed in this photo. I guess they didn't think to remove the older signs at the same time they installed the newer ones.
Suicide, 1952. Someone leapt to their death onto the freeway from the York Blvd. overpass.
Car accident death, 1952
Under construction in 1939.