The Miniplane was designed by the late Frank Smith of Fullerton, Calif., who built and flew the first one in 1956. Smith's original DSA-1 (the initials stood for Darned Small Airplane) is in the AirVenture Museum in Oshkosh, Wis., run by the Experimental Aircraft Association.
Here's a 1970 article by Budd Davisson on Smith's achievement:
The Smith Miniplane is right out of the back of every pilot's mind. It flies in the margins of notebooks and lands on the backs of napkins. We've all doodled something similar when our subconscious takes over and the "perfect" airplane flows out of the pencil. I'm sure, at one time or other, most of us have thought about our own personal little biplane. We've all dreamed, but somehow not many of us get past the doodling stage. Frank Smith did.