This is probably vestigial from before the interstate/numbering system: https://en.wikipedia.org/wiki/Southern_California_freeways#Freeway_names https://en.wik

This is probably vestigial from before the interstate/numbering system: https://en.wikipedia.org/wiki/Southern_California_freeways#Freeway_names https://en.wikipedia.org/wiki/Southern_California_freeways#F... > When Southern California freeways were built in the 1940s and early 1950s, local common usage was primarily the freeway name preceded by the definite article. It took several decades for Southern California locals to start to also commonly refer to the freeways with the numerical designations, but the usage of the definite article persisted. "Take the Ventura Freeway" -> "Take the 134"