At the February term of the Clinton County Common Pleas Court, held in 1877, a petition was presented by a number of the inhabitants of Dunnstable township, praying for the erection of a new township by the division of Dunnstable, which, on account of its great length and ill-shaped size, was inconvenient to a large number of its inhabitants.
The petitioners asked for a division of said township by a line commencing at a point on the northern bank of the West Branch of the Susquehanna river, where the southern end of the division line between Woodward and Dunnstable came to the river; thence in a southern direction through Great Island to low water mark on the souther side of Great Island; thence down the river to the northwestern corner of Wayne township. March 1st, 1871, the Court appointed George J. Eldrech, Jacob Quiggle and John Earon to inquire into the propriety of granting the said prayer. May 19th, 1877, the commissions made their report, recommending the said division.
The voters of Dunnstable township met on December 1st, 1877, and by a majority vote consented to the said division, and on December 10, 1877, the Court approved the division, and gave to the new township the name of Castanea. The township of Castanea is bounded on the east by Wayne township, on the south by Lamar, on the west by Allison, on the north by Woodward township and Lock Haven. It contains the village of Castanea, from which it derived its name.
Clinton County Genealogical Society (website) – specific page linked here