Those are both good sources to go to.
I am assisting the Japanese Tea Garden koi pond restoration project with some koi /pond issues here in San Antonio. Looking at some pre-WWII. photos There were some type of carp and maybe even koi in the pond before the war. Wheather they were truely koi or not is hard to determine from old and poorly preserved B/W photos. There were definately koi in the pond from the mid 60's when color photos were made. The historical societies says that koi have been in the pond since before WWII. Maybe I can find out more at some point.
Japanese Tea Garden, San Antonio, Texas on Flickr - Photo Sharing!
Here is a link to the Garden History