We present the recent results of a magnetometry survey of the Spring Lake Tract conducted during the summer of 2015 at Cahokia Mounds State Historic Site located along the Mississippi River Floodplain in southern Illinois. This tract, located southeast of Woodhenge and west of the Grand Plaza, is situated north of two known borrow pits and includes an additional, previously unidentified borrow pit. Through comparing our gradiometer results with our subsequent test excavations, we argue that this area of Cahokia potentially demonstrates an increase in building density at the Spring Lake Tract during the transition between the Terminal Late Woodland and Lohmann phases. In addition, our survey and exaction results demonstrate that this area was densely occupied between the Lohmann and Stirling phases. During the Moorehead phase, we identify a possible increase in habitation based on hypothesized structure density using statistical analyses of length and width ratios (m) and structure area (m2). Our preliminary results suggest that the Spring Lake Tract saw an increase in habitation during the Moorehead phase, a new perspective on the density and use of domestic space during Cahokia's late occupational history.
