California - LA

Hello! I am trying to locate a place. in 1920 Richar Melby and his family lived at 515 Stanford, the restaurant at 419 So Main. in Los Angeles. At the time, it was a restaurant. Is there a restaurant there today? In 1930, they are locatede at r411 S. Humphrey av. in the same city. and b411 S. Humphrey av. Where, and what is this? The adresses are taken from the LA city directory. In front of the adress, Richard O, has a title called "lab" Does anyone know what this stand for? Berta