Just did a little hunting and found this in Hollywood Remembered: An Oral History of Its Golden Age By Paul Zollo:
"Construction of a mammoth , curved concrete embankment commenced in August of 1923 and continued until December of 1924. At a height of 200 feet, it rose to a height taller than any other structure then standing in all of Los Angeles. Its crest was appointed with curved arches separated by a succession of stone busts depicting the California brown bear, which is featured on the state flag. Officially called Mulholland Dam by the city, Mulholland preferred for it to be know by a name that called attention no to the structure itself, but to the blue bayou that he had created in the canyon, Lake Hollywood."

P.S. Zollo
I still love the look of it looming when you can't see the water at all:

LAPL