Daniel A. Grant

In the century after the 1848 Treaty of Guadalupe Hidalgo drew the modern US-Mexico border, the Colorado River undermined the border's fixity and subverted the authority of both states to discipline borderland subjects. During this era, before dams regulated flows, the river paradoxically fixed territorial boundaries and shifted unpredictably across its floodplain, posing problems of jurisdiction and sovereignty when it no longer adhered to the boundaries it supposedly demarcated. In response, local indigenous and African-American communities who shared these dynamic boundaries formed alliances and negotiated conflicts among one another, the United States, and Mexico to remain rooted to their respective territories. Three interwoven case studies focusing on African-American squatters, Yuma Indians, and Cocopah Indians suggest that the river mediated racial belonging and exclusion long before contemporary water crises. Using archival and oral history methods, this dissertation reframes the history of settler colonialism in the borderlands as multiple, not binary.