“The RKO location ranch was located in Encino. It sported a complete western town with intersecting streets and a New York street. The Hunchback of Notre Dame set was there as well as a Hacienda set. A rail line ran through the property and was occasionally used for filming…
“The ranch was located approximately between Louise Avenue on the west, Balboa Blvd. on the east, Burbank Blvd. on the south, and Oxnard on the north, all in the city of Encino.”
Excerpt and undated* image from http://www.movielocationsplus.com/rkoranch.htm .
*likely from 1938 or 1939 as it looks like the cathedral from The Hunchback of Notre Dame is at the center right of the image.