The original township was bounded on the north by the Ohio River, on the east by the townships of Robinson and Cecil, on the south by Hopewell township, and on the west by the State of Virginia. It retained this large extend of territory for five years only. On January, 5, 1786, the inhabitants presented to the Court of Quarter Sessions of the Peace held at Washington an application for a division of Smith township. This application was favorably considered, and a certificate was sent to the Supreme Executive Council, and read before that body March 8, 1786. No action was taken upon the subject until September 2 of the same year, when it was again brought before the Council and confirmed. By this action that portion of the territory north of Harmon's Creek and north of Brush Run to the Ohio River was set off and named Hanover township. The original line dividing these townships ran "up Harmon's Creek to the source near Steven Smith's (the old McCurdy farm), thence across the ridge to the head of Brush Run, and down the run to Raccoon Creek." On the 11th of March, 1830, by order of court, the territory north of the present line between Smith and Hanover, not included in above, was set off from Smith township and attached to Hanover. Upon the erection of Mount Pleasant township, May 12, 1806, a portion of Smith was set off to from its territory. The eastern line of Smith at that time extended from near the present north point of Mount Pleasant township southward along the west line of Chartiers township, passing through Hickory, to the north line of Cross Creek, about one mile and a half south of that town.

The present boundaries of the township are Hanover township on the west, north, and northwest, Robinson on the northeast, Mount Pleasant on the southeast, and Cross Creek and Jefferson townships on the southwest.

Hanover is the extreme northwestern township of Washington County, having the county of Beaver and the State of West Virginia, respectively, for its northern and western boundaries. On the east it is bounded by Robinson and Smith townships, and on the south by Smith and Jefferson townships. The only streams of any size or importance belonging to Hanover are Raccoon and Harman's Creeks, which respectively mark parts of the eastern and southern boundaries of the township, and King's Creek, which flows in the southwesterly course across the northwestern corner of Hanover.

The territory now forming the township of Hanover was originally embraced in Smith township, and so remained for five years after the erection of the latter, Hanover being erected a separate township in 1786.