 Harold's interest in insects was soon replaced with an interest in American archaeology and, by 1924, he had become friends with A.V.Kidder, the noted archaeologist of the Southwestern United States; from this point on, Gladwin's work was in archaeology.Taking special interest in pottery shards and other refuse, Gladwin began to piece together theories on Hohokam culture as he excavated Casa Grande in 1927 in Arizona.