Episodic complexity and the emergence of a coastal kingdom: Climate, cooperation, and coercion in Southwest Florida

•Midden sediments were repurposed to raise mounds beginning ca. CE 1000.•A monumental structure was built and maintained ca. CE 1000–1570.•Constructed “watercourts” functioned to trap and store fish.•The Spanish fort of San Antón featured an early form of tabby construction.•Calusa resilience was based on innovative responses to historical contingencies. At European contact, the Calusa of southwestern Florida were the most complex society in Florida. For staple sustenance they relied not on agriculture, but on aquatic resources harvested mainly from shallow inshore bays. We summarize recently discovered physical evidence on Mound Key of mound-building, monumental architecture, large-scale food processing, watercourt construction and use, and the sixteenth-century Spanish fort and mission of San Antón de Carlos. We fold these findings into regional paleoenvironmental, archaeological, and historical knowledge, refining our understanding of Calusa history by examining it at smaller time increments. Following a diminished fishery during a significant drop in bay water levels near the end of the cool Vandal Minimum episode, the Medieval Warm Period reversed the situation and increased the productivity of the shallow waters, which provided food surpluses and new opportunities. After ca. AD 950, long-established cooperative heterarchical relations among coastal and inland polities gave way to coercive hierarchical relations. During the succeeding Little Ice Age, they intensified food production by engineering and maintaining “watercourts” that functioned as fish traps and short-term fish storage areas. Periods of overall prosperity were dampened by times of uncertainty, characterized by short-term, lowered water levels with reduced fisheries and renewed cooperative, heterarchical relations.