In 1804, Seneca County was formed by the splitting of Cayuga County. Then in 1817, in turn, a portion of Seneca County was combined with a piece of the remainder of Cayuga County to form Tompkins County.
In 1804 Seneca County was formed by the splitting of Cayuga County Then in 1817 in turn a portion of Seneca County was combined with a piece of the remainder of Cayuga County to form Tompkins County