Cumberland Township was one of the original five townships formed in the year 1767 in the western frontier of Cumberland County.
Of the five original townships, Cumberland was the smallest in overall size. Consisting of the region lying between Evitts Mountain and the Allegheny Mountain, with Wills Mountain running through the middle of it, the township basically consisted of two sixteen mile-long valleys.
Londonderry Township was formed in the year 1785 out of the western valley, i.e. the western half of Cumberland Township. Its own southwestern corner would be removed in 1795 when Somerset County was erected.
The township was named for County Derry (variously, Londonderry) in Northern Ireland. The name means 'oak-grove' or 'oak-wood'.
