I'll reveal the source after I hear if anyone knows about this photo .UPDATE! It now... appears.... as this is a photo of a model of 1850 Los Angeles and NOT a real photograph,
1850's - This is one of the earliest photos of Los Angeles, taken from a balloon. Looking northeast, the layout of the new city can clearly be seen with the Los Angeles Plaza located in the lower left-center. The large white structure to the left of the Plaza is the Old Plaza Church. The two streets running from bottom of photo to the Plaza are Main Street on the left and Los Angeles Street on the right. Alameda Street runs from the lower right corner diagonally toward the lower center of photo. The L.A. River can be seen running from the lower-right diagonally to the center of the photo, turns left and disappears behind the mountain. At that point the Arroyo Seco can be seen at its confluence with the LA River. The tall majestic San Gabriel Mountains stand in the far background. Vineyards blanket the area between the City and the L.A. River (lower right). The large dark spot in the lower-right of the photo is El Aliso, the historic landmark of the indigenous Tongva people who once lived in the Indian Village of Yangna at that location, adjacent to the L.A. River.
And don't forget my Saturday morning walking tours of historic Downtown Los Angeles! http://lacowboy.blogspot.com/2013/07/mid-70s-predicted-for-this-saturdays-2_23.html
And the excellent LA History photo site I found this is here. It is the third photo down on this page which is one of many,many pages of Los Angeles photos on the Water and Power Associates website. And scrol down for the LA History pages on their menu.
And here is the link to the site that says this is photograph of a model of 1850 Los Angeles - and not a real photo of LA. And here is a link to the overall site at USC. And here is another site that says the same thing.
And I became suspicious from the start since the houses lined up on Los Angeles Street were just too uniformly lined up - unlike any photo I have ever seen - plus there were not enough structures that were NOT on Main and LA Streets.
UPDATE - Does photo in this new post help explain this mysterious photo?