This report presents the results of magnetic gradient surveys covering 74.6 acres at the Great Circle and octagon of the High Bank Works earthwork site, a unit of Hopewell Culture National Historical Park in Ross County, Ohio. The Great Circle survey was conducted under contract with the Midwest Archeological Center and the octagon survey is the result of a collaboration between Ohio Valley Archaeology, Inc., the Cleveland Museum of Natural History, The Ohio State University, and Hopewell Culture National Historical Park. To date, all of the ground around the Great Circle (46.3 acres) has been surveyed and 28.3 acres of the fields containing the octagon have been covered. The magnetic surveys have detected many anomalies of archaeological interest, including the main earthwork embankments, one probable and another possible small enclosure, feature clusters at the centers of the Great Circle and the octagon, and hundreds of possible pit and posthole features spread all across the survey area. Some of the possible pits, including several that appear to be especially large, fall along important lines of astronomical observation identified by Hively and Horn (1984). The report concludes with a further discussion of the results and suggestions for additional work, including geophysical survey and ground-truthing techniques.

This report presents the results of a large-area magnetic gradient survey at Hopewell Mound Group, a unit of Hopewell Culture National Historical Park in Ross County, Ohio. The survey was conducted by Ohio Valley Archaeology, Inc., under contract with the Midwest Archeological Center, National Park Service, during 18 days of work spread across the period from October 18, 2012 through March 27, 2013. Along with an additional 3.1 acres of data collected in September and October of 2011, the results presented here cover 73.4 acres of the eastern half of the site on the lower terrace (the landform containing the bulk of the earthworks). Hundreds of magnetic anomalies of potential archaeological interest were detected during the magnetic surveys, including known features from nineteenth century maps that have since disappeared from the ground surface (e.g., the square) and many other new features of interest. Chief among these new features are a post circle and central pit cluster within the medium-sized circle, a cluster of pits located outside the small circle detected in 2001, a complex of features associated with Mound 4, at least four possible burned structures just north of the square, and one or perhaps two possible prepared/burned surfaces or floors located near the main enclosure wall to the south of Mound 1. Many other anomalies detected during the survey are associated with possible cultural or landform features that are not fully understood. Two long linear features could be natural linear depressions or soil borrow features intermittently filled with refuse. Numerous large-area positive anomalies appear to be arranged in an oval pattern to the north of the square. The source of these large anomalies is uncertain. In addition to providing numerous maps of the results and an appendix containing information about anomalies of interest, several recommendations for additional kinds of geophysical survey and ground-truthing work also are presented.