Interstate 405 is the San Diego Freeway—an interesting name, because it doesn’t go to San Diego.
I was once a local, family members are local, and we always called it the Freeway!
I wouldn’t know.
Well, if your’e going to San Diego, you do usually get on the 405 which merges into the 5 which does go to San Diego—but the 5 already had a name, the Santa Ana Freeway, because back in the day when they were naming the freeways (before the interstate system was created) that’s all the farther it went.
You can get to San Diego the old fashioned way on Pacific Coast Highway—used to be US 101—now Cal 1.
It is because it roughly corresponds to the western route laid out in the 1955 plan which went all the way down toward San Diego.