Twenty Thousand Leagues Under the Sea, 1914:
"Yet," Conseil asked me, "doesn't master believe in gigantic devilfish?"
"Yikes! Who in Hades ever believed in them?" the Canadian exclaimed.
Industrial World, Volume 46, Issue 2, 1912:
"Are you going up to the roof? Will you take a message to someone for me, Anne? I promised to meet an intern up there."
"Yikes! Who?"
I'll observe that the above uses appear to be using "yikes" not to indicate fear/alarm, but rather simple surprise. (I can't really thinks of any modern word that might be used in this context, aside from the rather bland "Oh!?", or maybe "Wow!".)