I know this is an old thread, but I may have at least some info on Kaplans in Iowa.
I have not started that side of me tree yet, but...
My grandfather was Max Kaplan, son of Joseph. Joseph was born in Minsk, Russia, and immigrated to Ellis Island in roughly 1902-1904, with a few children. Joseph and Max (don't know how many others) moved to Iowa sometime after. Max eventually moved to Pittsburgh, PA.
Feel free to contact me for more info, but it may take a few days to get back, as I have to pull names and dates from family members.
Hope this helps someone in there search.