Under the National Historic Preservation Act of 1966, federal agencies must consider how their properties might affect historic places such as buildings and archaeological sites. Archaeological and historical investigations along the WIS 57 corridor followed Section 106 procedures that included identifying historic resources, evaluating affected resources, determining historic significance, avoiding sites through redesign when possible, and mitigating significant sites that could not be avoided. Investigations began in 1992 and continued through 2008, identifying 107 archaeological sites, testing 78, finding 38 significant, avoiding 30 by rerouting the highway, and mitigating eight that could not be avoided. Phase I involved reviewing records and background materials and conducting pedestrian reconnaissance to locate previously recorded and unreported historic and prehistoric sites near the study area. Phase II evaluated sites likely to be disturbed, using hand and machine-aided excavations to determine whether they were potentially eligible for the National Register of Historic Places and therefore significant. Phase III addressed significant sites or buildings that could not be preserved by carefully recording them before ground disturbance, typically through large-scale controlled excavations designed to sample rather than completely excavate a site. During construction, archaeologists also monitored ground-disturbing activities in culturally sensitive areas to help prevent incidental disturbance of human remains through close cooperation among WisDOT, contractors, and archaeologists.