From Ohio History Central
Ohio is commonly referred to as the Buckeye State due to the prevalence of Ohio Buckeye trees within the state's borders. In 1953, the Ohio legislature designated the ''Aesculus glabra'' or the Ohio Buckeye as Ohio's official state tree. The tree is called the buckeye tree because its nuts resemble the shape and color of a deer's eye. The buckeye tree is relatively common to Ohio, growing especially well along rivers and streams and in floodplains.