It's worth going to the site that the MH Nerd links to before going to the LAPL site because the poster of the pictures on his Flickr page gives an explanation of how they came to be, in true City Nerd fashion. I applaud this discovery by Gerard Van der Leun and the revelation of such by the Montecito Heights Nerd.
Update1: I have to also give credit to the Los Angeles Public Library and Carolyn Cole for the work in preserving the "Photos of LA." This resource is one of the best ways we can reach our past in this City, and without the work Carolyn and the library does on our behalf, we wouldn't have the understanding (as limited as it is) of where we came from and where we're going.
Thanks to a note from the tracker of all things news (LA Observed), I was pointed to another fairly recent post about these Ansel Adams pics from Ms. Kellogg at LAist.
Notice how, in 1940, the City used reflectors along the crosswalk lines.
(photo from LAPL via Flickr)