If you played LA Noire, you probably had the feeling the studio had put in a lot of work like this to recreate a past version of Los Angeles for the game. (That, and they seem to have hired pretty much the entire cast of Mad Men.)
I just read Time and Again, in which time travel was effected in part by finding places that were essentially unchanged from the target time period. It’s sometimes surprising just how much of the past has remained, even in a place that has changed as much as LA has from when it was just a Spanish mission town on the river1 to the modern monstrosity it is today.
Its original name was apparently not the absurdly long “El Pueblo de Nuestra Senora La Reina de Los Angeles de Porciuncula” (which is what Wikipedia still cites as the full name) but simply “El Pueblo de la Reina de Los Angeles”. Either way, it’s pretty obvious why we call it Los Angeles or even LA today.