Consolidation of populations and incipient political centralization characterize the period, particularly in the Eastern Woodlands and the Southwest. The success of food crops such as maize and beans allows for meaningful concentrations of peoples. Settlements are enlarged along local patterns, with individual centers assuming regional dominance. Cahokia on the Mississippi River floodplain of Illinois expands; its over 100 earthen mounds are used for varying purposes. Important Mississippian sites in the Southeast such as Moundville, Spiro, and Etowah show clear evidence of high-ranking inhabitants with many precious objects in their burials. In the arid Southwest, where the sophisticated influence of Mexico to the south is felt, numerous centers become large only to be abandoned. In the far north, the pan-Arctic Thule culture begins in Alaska and rapidly spreads eastward.