The scene above is somewhere on Sunset Boulevard (I'm guessing just east of Figueroa), in the 1940s, found here. And below, the same block, 20 years later, the buildings decimated and the ghostly retaining walls now covered in gang 'placas', "mostly from the Alpine gang."
Both images are from this fascinating Flickr set The Golden Age of Gang Graffiti, which I found via stylish-cool Tagbanger. "This is, of course, still vandalism," the page by KID DEUCE says, "but from an earlier and more innocent time." Enjoy, especially the last shot of an elegantly threatening chola.