North American Database of Archaeological Geophysics

Abstract/Summary:

Project Name: Johnson's Island Confederate Stockade Cemetery, Sandusky Bay, Ohio;

Reference: Johnson, W.J., D.W. Johnson, G. Gozdzik (2001). Geophysics Comes of Age in North American Archeology. Paper Presented at Society of American Archaeology, 66th Annual Meeting, New Orleans, Louisiana, April 18-22, 2001.

From 1862 until 1865, a small island in the Sandusky Bay of Ohio's Lake Erie served as a prison for Confederate soldiers captured during the Civil War. During this time an approximated 305 prisoners died while incarcerated on Johnson's Island shores. Most of the dead were buried within the prison compound with wooden markers as tombstones. The current stone markers were not erected until the United Daughters of the Confederacy restored the cemetery in 1890. The current number of headstones only amount to 206. An estimated 25 to 30 bodies had been returned to families and were not located in the cemetery, but that still left around 70 unaccounted graves somewhere on the island.

In May of 2000, D'Appolonia archaeologists conducted a ground penetrating radar survey in the area of the known Confederate cemetery on Johnson's Island. The survey was able to cover approximately 95% of the area containing tombstones. Most graves were believed to be within 3 to 4 feet of the surface due to the shallow bedrock on the island. The cemetery was divided into 4 survey blocks based on previous survey. A RAMAC GPR system with a 200 MHz transmitter and antennas (bi-static mode) was used to conduct the survey. Measurements were triggered every 0.2 feet by way of tracking wheel and readings were taken 16-fold stacking.

The survey produced a number of anomalies that are strong indications of graves. Very prevalent anomalies are representative of graves containing air-filled or metallic coffins. There is a poor correlation between the grave markers and the actual graves. One area contains a large number of graves and indicates mass burial while another section has much more pronounced anomalies indicating coffins. A total of 242 possible graves were recorded with the GPR survey. Fifteen are well defined due to possible coffins. Soil disturbances indicate another 101 possible graves, while less defined soil disturbances define the other 126 graves.

Interpreting GPR imagery can be challenging. Variations within the subsoil and bedrock can cause readings that may be mistaken as graves. However, the number of anomalies is similar to the amount of assumed graves. It is also possible that a number of graves are present in the unsurveyed portion of the cemetery, and just outside of the current boundary.

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