In addition to building roads, causeways, canals, dikes, reservoirs, mounds, raised agricultural fields, and possibly ball courts, Erickson has argued, the Indians who lived there before Columbus trapped fish in the seasonally flooded grassland. The trapping was not a matter of a few isolated natives with nets, but a society-wide effort in which hundreds or thousands of people fashioned dense, zigzagging networks of earthen fish weirs (fish-corralling fences) among the causeways.
