Historian Michael Beschloss posted this image to his Twitter feed on Sunday and said it was of Venice Beach in 1947. No origin or backstory. His Twitter page says there's a website on the way that will give the origins of the dozens of photographs he has posted recently. Some of his caption info hasn't been quite right. Earlier this month he posted a photo of the old Brown Derby restaurant at Wilshire and Alexandria but mislabeled it as the "original" Brown Derby, which was actually in the next block to the west and didn't look quite like the one seen in his photo. The one pictured would be more accurately called the last Brown Derby in that stretch of Wilshire.
Monday update: Looks like Beschloss got this one wrong too. Peter McAndrews emailed to say the buildings in the purported Venice photo are opposite the original Muscle Beach in Santa Monica. Sure enough, a building that looks like the one on the right shows up right now on Google View, facing the Santa Monica Chess Park.
Anyway, Beschloss this weekend also posted this photograph of UCLA's first buildings in Westwood under construction circa 1928. He indicates this one is from the Works Progress Administration, but that's a good bit earlier than the WPA came along (the Depression hadn't even really begun yet) so who knows.