I recently found some more family photos. Unfortunately, most of them aren't labeled - including this one:
There is a flag of California in the picture, but I cannot place it further. I'm thinking the Bay Area, maybe Golden Gate Park? Another possibility is the fact that the 1915 World's Fair was held in San Francisco, though I think this might have been taken later than that (based on the clothing).
Anyone with any knowledge (or guesses) of this place, please contact me - I'd really appreciate any clues!