Much has been debated about the presence of undocumented workers along the South Texas border, but these debates often overlook the more complete dimension: the region's longstanding, undocumented economies as a whole. Borderlands commerce that evades government scrutiny can be categorized into informal economies (the unreported exchange of legal goods and services) or underground economies (criminal economic activities that, obviously, occur without government oversight). Examining long-term study, observation, and participation in the border region, with the assistance of hundreds of...