Unadilla was at first known as "Milan". A post office was established in June 1834, but because Milan, Michigan, already had the name, the post office was called "Unadilla" after the township. But a plat had already been recorded for the "Village of Unadilla" in what is now Williamsville, so the plat was recorded as the Village of East Unadilla. This became known as simply "Unadilla" after the other village of Unadilla was abandoned. A survey for the plat was made on April 14, 1837, by Richard Peterson, Jr., but it was not recorded by the proprietors Robert Glenn and Thomas S. Gill until April 21, 1840. [Wikipedia]