Friday, August 18, 2017

The Petroglyphs of Pennsylvania: Rock Art in the Lower Susquehanna River Valley

Did you know that the Lower Susquehanna Valley, approximately 50 miles south of Harrisburg, Pennsylvania, is home to one of the largest concentrations of prehistoric petroglyphs in the Northeastern United States?

Petroglyphs are a form of rock art in which images are pecked or carved into the surface of a rock. In the case of Pennsylvania’s petroglyphs, rocky outcrops along rivers were prime locations where these images were created. Petroglyphs can be found across Pennsylvania and styles vary widely depending upon the area in which they were created. Nearly all the petroglyphs recorded in Pennsylvania (42 sites at time of writing) are associated with rivers. Waterways were, and still are, significant features of the natural landscape that have shaped where people lived and how they traveled since long before the first Europeans settled in this area.

The distribution and various styles of petroglyphs in Pennsylvania.

The petroglyphs south of Harrisburg, PA (numbers 8 and 9 on the above map) are particularly special due to their location in the center of the nearly mile-wide Susquehanna River. Some groups of petroglyphs in this area, such as those on Walnut Island and nearby Creswell rock were submerged underwater when the Safe Harbor Dam was constructed in the early 1930s. Other sites farther downstream such as Big and Little Indian Rock are accessible only by boat, a feature that has no doubt helped preserve the numerous rock carvings that were made by the prehistoric people who once inhabited this river valley.

It is difficult for us to imagine the vastly different landscape of the Susquehanna River prior to the construction of railroads and hydro-electric dams. The river was at one time filled with rocky outcrops, small islands, and numerous rapids carved by the ancient waters of the Susquehanna, one of the oldest rivers in the world. The riverscape prior to the construction of the Safe Harbor Dam is reflected in photos taken prior to the dam’s construction, as well as by maps made by various surveyors during the 19th century.

A composite image of the Susquehanna River before and after construction of the Safe Harbor Dam. Walnut Island is in the group of islands on the left side of the upper image.
(top image: Scott’s Map of Lancaster County, Library of Congress; lower image: Google Earth)

In 1930-1931, an expedition led by Donald Cadzow documented four petroglyph sites in the Safe Harbor area where Conestoga Creek flows into the Susquehanna River: Little Indian Rock, Big Indian Rock, Walnut Island (now submerged), and Creswell Rock (now submerged). The team photographed and drew the petroglyphs of Walnut Island and Creswell Rock before ultimately drilling the petroglyphs from the surrounding rock on which they were created and transporting them to the State Museum of Pennsylvania. Four of the petroglyphs from Walnut Island are on permanent display at the State Museum’s Archaeology Gallery in Harrisburg, and another four panels are on display at the Conestoga Area Historical Society Museum in Conestoga, PA. The remainder of the petroglyph panels removed from Walnut Island and Creswell Rock remain in storage at the State Museum of Pennsylvania.

The Petroglyphs on Walnut Island were traced and photographed before being drilled from the surrounding bedrock. The original section of rock with the pecked image is on display at the State Museum of Pennsylvania’s Archaeology Gallery. (Image: PHMC)

Like much of the archaeology performed during the first half of the 20th century, documentation and collection practices fall short of today’s standards. Although Cadzow and his team recognized the importance of the individual images, other information, such as the exact directional orientation of the glyphs and the shape and nature of surrounding rock formations, was largely neglected. Additionally, some fruits of their efforts, such as creating casts of the petroglyphs, have been discarded in the decades since the work was undertaken. The documentation that exists today falls short of depicting the full stunning beauty of a place that no doubt held special significance to the people who created these images.
Donald Cadzow’s map of petroglyphs on Walnut Island. The image panels depicted on this map are the best evidence researchers have of their original locations on the island. (image: Cadzow 1934, PHMC)

Many of the petroglyphs located on Walnut Island bear little resemblance to the petroglyphs of other rock art sites within the Northeastern United States, and researchers have long pondered their origins. Other sites near Safe Harbor, such as Little Indian Rock and Big Indian Rock are similar in style to petroglyph sites attributed to Algonkian groups which inhabited much of the Northeast and Canada during Woodland and Late Prehistoric times.
While the meaning of petroglyphs is still largely unknown, advances have been made in understanding their significance as places of teaching or for communing with spirits who were believed to inhabit sacred locations associated with rocky outcrops and water. Some believe that the petroglyphs are reflections of the sky above.
One of the abstract groups of petroglyphs on Walnut Island. This rock outcrop provided a view of the river looking towards Lancaster County. (image: PHMC)

Donald Cadzow’s report of his expedition is published as a book under the title Petroglyphs in the Susquehanna River near Safe Harbor, Pennsylvania. It is available for purchase from the PA Heritage book store.
If you visit a petroglyph site, there are steps that you can take to help preserve this fragile and non-renewable resource for future generations. Researchers today have no way of knowing what techniques may be developed in the future that could contribute to the understanding of these ancient writings.
The following guidelines for visiting petroglyph sites are adopted from the National Park Service:
-          Do not touch the petroglyphs, even small amounts of oils from your hands can darken and destroy the carved images
-          Photograph and sketch the images, but avoid taking rubbings which can hasten the deterioration of the petroglyphs. The best time of day for viewing petroglyphs is early morning or evening, when the Sun is low on the horizon.
-          Do not introduce any foreign substance to the rock surface such as paint or chalk, these actions can damage the image.
-          Do not repeck, recarve or deface the images in any way, these actions destroy the original image. Many rock art sites have been destroyed by the addition of historic graffiti.

Petroglyphs in Pennsylvania, videos produced by the PHMC:
Petroglyphs of Pennsylvania Part I - 
Petroglyphs of Pennsylvania Part II
Additional information on petroglyphs is available through our web site:

Additional Resources:
Diaz-Granados, Carol, and James R. Duncan, eds. The rock-art of eastern North America: Capturing Images and Insight. Vol. 45879. University of Alabama Press, 2004.
Cadzow, Donald A. Petroglyphs Rock Carvings in the Susquehanna River Near Safe Harbor. Pennsylvania... Vol. 3. No. 1. Pennsylvania Historical Commission, 1934.
Lenik, Edward J. Making pictures in stone: American Indian rock art of the Northeast. University of Alabama Press, 2009.
Vastokas, Joan M., and Romas K. Vastokas. Sacred art of the Algonkians: A study of the Peterborough Petroglyphs. Mansard Press, 1973.

Carr, Kurt W. and Nevin, Paul A., Advanced Technology Rubs Ancient Past. Pennsylvania Heritage, Vol. XXXIV, No. 4, Fall 2008 (

For more information, visit or the Hall of Anthropology and Archaeology at The State Museum of Pennsylvania .

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