The original Torrance City Hall on Cravens Avenue was designed by architects Walker & Eisen and built with WPA funds in 1936. The City Hall was an efficient, standard moderne building that served for 25+ years--with no mosaic. That came later.
Walker & Eisen were a well-known and successful firm by the 1930s. They actually helped construct the Oviatt Building in on 6th and Olive in Los Angeles--now the Cicada Restaurant. According to PublicArtInLA, they were "primarily responsible for the shell of the building and the Olive Street facade. Percy Augustus Eisen (1885-1946) and Albert Raymond Walker (1881-1958) were in partnership from 1919 to 194-. . . . Their later works were mostly government buildings, theaters, and branch facilities carried out in the moderne style. Major commissions included the Fine Arts Building (1925), United Artists Building (1927), Title Insurance Building (1928), National Bank of Commerce (1929), Fruit Growers Exchange (1934), Beverly-Wilshire Hotel (1926), El Cortez Hotel (San Diego, 1927), El Mirador Hotel (Palm Springs 1927), Mar Monte Hotel (Santa Barbara 1927), Torrance City Hall, Jail, and Municipal Building (1936), . . . " (text prepared by Martin Eli Weil, A. I. A., Restoration Architect, for Ratkovich, Bowers Incorporated, October 1982, for nomination of the building to the National Register of Historic Places.)
Well, that confirms a story I've heard from people who grew up in Old Torrance--that the basement served as a jail. Children who walked by the City Hall on their way to school in the 1950s and early 60s remember that the prisoners would call to them from small, sidewalk-level windows: "Hey, kids! Let us out of here!"
By the 1970s, a new, bigger-by-a-factor-of-maybe-twenty City Hall complex was built and the old building became a Home Savings. That's when this mosaic was added. I have not been able to confirm that the work is Millard Sheets'--the Torrance Historical Society and the main library weren't sure, and the local newspapers are not indexed or online.
However, I'd put five bucks on it being Sheets' handiwork. In fact, I believe there were once more mosaics, but this is the only one that remains on the outside. Home Savings moved away in the 80s, and the building is now the local office of Time Warner Cable.