Little attention has been paid thus far to explaining either the different rates of cultural change in the archaeological record of the Northern Plains of North America or the epistemological relationship between the prehistoric and historic pasts of the area. These two problems are examined by combining Braudel's conception of time with more recent Annaliste explications of the relationship between structure and event. With specific reference to the later prehistoric and early historic record of southern Alberta, Canada, structures of mentalite are defined in prehistoric processing and procurement activities and traced into historic period gender relationships. Geographical structures are identified in subsistence activities. These structures were transformed through a recursive relationship with human action, manifested in specific events: the adoption of the bow and arrow and ceramics, and the arrival of European cultures. By denying the existence of the prehistoric and historic pasts as epistemologically separate entities, archaeology may be used to amplify specific ethnographic and historical studies, rather than the other way around, as is usually the case.