The Classificatory-Historical period took place from 1914-1960 and marked a time concerned with chronology and dating. Universities and other research institutions emphasized time as the primary tool of classifying North American cultures. During this time period it was thought that cultures could be well understood based on the chronological ordering of events. An important technique developed during this time was stratigraphic excavation, which was the differentiation and examination of different layers of earth. Stratigraphic excavation operates on the principle of deeper layers being older than more shallow layers and is helpful with dating layers of earth and the artifacts within them. This technique was used extensively for the dating
