Gahanna was founded along the Big Walnut Creek in 1849 by John Clark of Ross County from 800 acres of land that his father, Joseph Clark, had purchased from Governor Worthington in 1814. Clark named his property the Gahanna Plantation, from which the City of Gahanna derives its name. The name Gahanna is derived from a Native American word for three creeks joining into one and is the former name of the Big Walnut Creek. The City of Gahanna's Official Seal refers to this confluence of three creeks with the inscription "Three In One".
Gahanna has been listed as one of the Top 100 Best Places to Live in 2007 by Money magazine.