In an integrated geological, archaeological, and geophysical study in the New Madrid seismic zone of the southeastern United States, we documented a prehistoric sand blow and related feeder dikes at an archaeological site near Steele, Missouri. Archaeological analysis combined with radiocarbon dating suggest that the earthquake-induced features formed between A.D. 1400 and 1670. This paleoseismic study provides the best evidence to date for a large earthquake occurring in the zone within ∼400 yr prior to the 1811–1812 New Madrid earthquake sequence. To determine an optimal location for excavating at the study site, we mapped surficial artifact density and conducted geophysical surveys. In doing so, we were able to reveal critical relationships for constraining the age of the prehistoric earthquake with minimal impact to the archaeological site.