Walpack Township is located in the scenic western section of Sussex County, along the Delaware River. The township includes a section of the Old Mine Road, which is reputed to have been constructed by the early Dutch miners in the mid-1600s as a means of transporting copper ore from the Pahaquarry area to Kingston (formerly Esopus), N. Y. At one time it was considered the longest commercial road of note in the colonies. The area was sparsely settled before 1736.
Walpack Township was originally much larger when it was part of Hunterdon County in 1731. Walpack became part of Morris County when that county separated in 1739. When Sussex County was established in 1753, Walpack comprised what is now Sandyston and Montague Townships in Sussex County and Pahaquarry (now Hardwick) in Warren County. It became the present size in 1824 when Warren County separated from Sussex County.