The hill may not be visible in that pic, but the Signal Hill area, including much of the hill itself, was once covered with a forest of oil derricks. There were so many derricks that local wags took to calling it “Porcupine Hill” in the '20s.
Google Image Search: Signal Hill Oil Derricks
As for the name, Signal Hill came to be known as Signal Hill long before it had electronic comm towers.
John Rockwell of the US Coast Survey erected a signal atop the hill during the 1889-90 survey that established the Los Angeles Baseline. In 1905 he wrote in a letter:
I recognize a hill near the town on which I erected a signal and which bears the name of Signal Hill to this day.
The name became official when the city of Signal Hill was incorporated in 1924, after the discovery of oil in 1921.
The photo is most likely part of the City of Signal Hill, even though the hill itself isn’t visible.
