Pennsylvania Route 666 is an east–west state route located in northwest Pennsylvania. The western terminus of the route is at U.S. Route 62 (US 62) in the Hickory Township municipality of East Hickory, and its eastern terminus is at US 6 in the hamlet of Sheffield. It cuts through most of Allegheny National Forest, and is therefore sparsely populated, with the largest settlement along the road being Endeavor. Its official name is the David Zeisberger Memorial Highway.

Hickory Township is a township in Forest County, Pennsylvania, United States. As of the 2020 census, the township population was 416, a decline from 558 in 2010.