The sign was erected in 1923 and originally marked “HOLLYWOODLAND”. Its purpose was to announce the name of the new development of separate housing in the hills above the Hollywood neighborhood of Los Angeles.
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Notice the ad for a bomb shelter at the 4:20 timestamp.
Source: https://rarehistoricalphotos.com/los-angeles-street-scenes-1930s/
There are some great 'then and now' photos there.