A GEOPHYSICAL INVESTIGATION OF THE PARADE GROUND AT FORT JEFFERSON DRY TORTUGAS NATIONAL PARK, FLORIDA National Park Service Southeast Archeological Center U.S. Department of the Interior Tallahassee, Florida 2008 SOUTHEAST ARCHEOLOGICAL CENTER The Southeast Archeological Center (SEAC) is a support operation of the National Park Service’s Southeast Region. In assisting parks with their cultural resource management needs, SEAC facilitates long-term protection of archeological resources and compiles and utilizes the archeological information obtained from these resources. In addition to annually generating numerous archeological reports, as mandated by federal law and park operations, SEAC is the repository for over six million artifacts that make up the Southeast Region’s research collections and contribute to its cultural database. SEAC is staffed by professional NPS archeologists and regularly employs archeology students from Florida State University and other anthropology programs throughout the Southeast. For more information contact: Southeast Archeology Center 2035 East Paul Dirac Drive Johnson Building, Suite 120 Tallahassee, Florida 32310 Telephone: 850-580-3011 Fax: 850-580-2884 http://www.cr.nps.gov/seac/seac.htm A Geophysical Investigation of the Parade Ground at Fort Jefferson Dry Tortugas National Park, Florida SEAC Accession 2099 DRTO Accession 159 by Charles F. Lawson National Park Service / Southeast Archeological Center / Tallahassee, FL / 2007 Management Summary In December of 2006, the Southeast Archeo- historic refuse dumps. In addition, numerous logical Center (SEAC) conducted a ground historic and modern sewage, electrical, and penetrating radar (GPR) survey at Fort Jef- water distribution utilities were identifi ed dur- ferson in Dry Tortugas National Park (DRTO). ing the survey. The survey was designed to include all open Prior to initiating the fi eld portion of the and clear ground surfaces of the fort’s parade radar survey, historic maps drawn during the ground, and a limited area outside the fort’s construction and military occupation of the walls in the campground and picnic area. The fort were collected and digitized into a geo- goal of the project was to identify subsurface graphic information system (GIS) that was historic features that could be imaged using used to predict the locations of, and later to GPR and to provide maps of these features to interpret, anomalies identifi ed during the GPR the park to aid in the management and protec- survey. Upon completion of the survey, highly tion of buried historic fabric at the fort. Just accurate mapping of the fort’s interior and over fi ve acres (20,500 square meters) of Fort exterior was carried out using a global position- Jeff erson’s parade ground, and 2,450 square ing system (GPS) and a total station. The map meters (.61 acres) of land outside the fort’s produced was used to further refi ne and adjust walls, were surveyed with the GPR. The parade the original GIS, and provided an accurate base ground survey coverage represents 63.4 per- map upon which historic maps of the fort and cent of the full eight acres of interior space at the results of the GPR survey could be overlaid. the fort, but most of the unsurveyed property The end result is a layered GIS database/map was covered with existing buildings, ruins, or showing accurate locations of extant and relict impenetrable vegetation. historic features in real world coordinates that A variety of historic subsurface features no can be referenced on the ground and navigated longer visible on the modern ground surface to using a GPS unit. were revealed during the radar investigation. This document includes a brief construc- These included relict footpaths and roads, tion history of the surveyed areas at Fort Jef- possible privies and/or cisterns, a probable ferson, maps and images produced by the GPR grave, foundation remains of extinct buildings survey and GIS exercise, and an archeological (the original lighthouse and other possible his- interpretation of the data collected during the toric structures associated with the lighthouse survey. The electronic data used in the creation keeper’s home and temporary structures that of the GIS has also been provided to DRTO on were in place during the construction of the a DVD so that it may be incorporated into the fort), as well as a number of buried anomalies park’s resource management database. of unknown origin probably associated with 2 Contents MANAGEMENT SUMMARY .........................................................................................................2 ACKNOWLEDGMENTS ..................................................................................................................7 CHAPTER 1. INTRODUCTION ........................................................................................................8 CHAPTER 2. A BRIEF CONSTRUCTION HISTORY OF FORT JEFFERSON’S PARADE GROUND ...11 CHAPTER 3. HISTORIC MAP ANALYSIS ......................................................................................18 THE TEMPORARY STRUCTURES ..........................................................................................................19 THE LIGHTHOUSE STATION ...............................................................................................................19 CONSTRUCTION DISTRIBUTION ROUTES ................................................................................................24 SUMMARY ...................................................................................................................................24 CHAPTER 4. GROUND PENETRATING RADAR SURVEY .............................................................28 GPR QUADRANT 1: GRIDS 1, 4, 16, & 12 ......................................................................................33 GPR QUADRANT 2: GRIDS 2, 3, & 5 ..............................................................................................38 GPR QUADRANT 3: GRIDS 17, 18, 19, 20, 21, & 23 ......................................................................44 GPR QUADRANT 4: GRIDS 24, 25, & 26 ........................................................................................50 GPR QUADRANT 5: GRIDS 11, 13, 14, & 15 ..................................................................................50 GPR QUADRANT 6: GRIDS 6, 7, 8, 9, & 10 ....................................................................................61 GPR QUADRANT 7: GRIDS 21, 22, 27, 28, 29, 30, 31, 32, 33, 34, 35, & 36 ..................................65 GPR QUADRANT 8: OUTSIDE THE PARADE GROUND, GRIDS 37, 38, 39, 40, & 41 ..................................68 CHAPTER 5. CONCLUSIONS AND RECOMMENDATIONS ..........................................................74 APPENDIX 1. DIGITAL DATA .......................................................................................................84 REFERENCES CITED .....................................................................................................................85 3 Figures Figure 1. The location of Fort Jefferson, in the Dry Tortugas National Park............................. 9 Figure 2. The project area at Fort Jefferson. ...........................................................................10 Figure 3. Plans for the parade and fi rst tier of Fort Jefferson, as designed by the Board of Engineers in 1887. ............................................................................................................ 13 Figure 4. Portion of an 1850 map of Garden Key showing completed and pending construction and the location of temporary structures at Fort Jefferson. ........................ 15 Figure 5. Map of Garden Key conditions in 1861. ..................................................................... 16 Figure 6. July, 1848 conditions on Garden Key. .........................................................................20 Figure 7. Geo-rectifi ed version of a map depicting the conditions on Garden Key in 1850. .21 Figure 8. Geo-rectifi ed version of a map depicting the conditions on Garden Key in 1854. .22 Figure 9. Geo-rectifi ed version of a map depicting the progress of work at Fort Jefferson in1861. .................................................................................................................. 23 Figure 10. Pre-1872 image of the sally port entrance to Fort Jefferson’s parade ground. .... 24 Figure 11. Geo-rectifi ed version of an 1887 map of the second (1872-1912) lighthouse keeper’s residence. ................................................................................................................ 25 Figure 12. Image of the west side of the 1872-1912 lighthouse keeper’s quarters. ...............26 Figure 13. The Italy grave and Major Smith Monument in 1937. ............................................ 26 Figure 14. Geo-rectifi ed map of the construction distribution routes at Fort Jefferson in 1861. .................................................................................................................. 27 Figure 15. GPR results from the complete survey inside and outside of the fort at 30 to 50 centimeters below the surface. ............................................................................. 30 Figure 16. GPR results from the complete survey inside and outside of the fort at 50 to 90 centimeters below the surface. ............................................................................. 31 Figure 17. Location of GPR Quadrant 1. ....................................................................................34