Dendrochronology of the Pennsylvania Main Line Canal Lock Number Four, Pittsburgh

Abstract

Well-preserved timbers and planks were excavated from Lift Lock No. 4 of the Pennsylvania Main Line Canal, built in Pittsburgh ca. 1829. The discovery of these extensive buried remains afforded an opportunity to explore the applicability of dendrochronological and dendroclimatological research to eastern United States mesic sites of the historic time period. Eighteen samples of white pine ( Pinus sp.) planks were analyzed using a tree-ring dating program to develop a floating (undated) chronology for the site. Eleven of the sampled planks were found to match at significant values to form a 152 year-long floating chronology. The floating chronology was then cross-dated with a white pine master chronology from Cook Forest, Pennsylvania. The dendrochronological work shows that trees used in building the canal lock began to grow by AD 1658, while the outermost extent rings date to AD 1809. The established dendrochronological sequence is interpreted with respect to lock construction, and the implications of the evidence for environmental interpretations are also discussed.