Urrea reveals the vigilance at the core of work of the Border Patrol. The drags they create not only help agents track the walkers, they also tell the story of the walkers’ journey. Drags allow Border Patrol agents to tell where walkers are coming from, where they’re headed, and what their condition is. Urrea, who is himself very interested in the journeys of those who attempt to cross this desert, is all too aware of the ways in which these histories are often impossible to recover. Therefore, he’s intensely interested in the methodologies employed by Border Patrol to “read” the landscape for signs of the immigrants’ comings and goings, which are otherwise so often swallowed by the desert and lost to history, leaving the “illegals” nameless.