The Disappeared report series is collaborative project between two Tucson-based organizations, La Coalición de Derechos Humanos and No More Deaths. Between Derechos Humanos’ 20 years of community work, including the 24-hour Missing Migrant Crisis Line, and No More Deaths’ 12 years of humanitarian aid in the Arizona backcountry, we have witnessed and listened to thousands of stories of border crossings throughout Southern Arizona. Our research goals are transformative: to expose and combat those US government policing tactics that cause the crisis of death and mass disappearance in the borderlands. In this first report, we find that people who cross the border and are never seen again do not merely go missing, they are disappeared by the US border-enforcement system. Using surveys from Nogales and data from the Derechos Humanos Missing Migrant Crisis Line, we find that the Border Patrol routinely chases border crossers into remote terrain causing them to scatter, become lost, and often die or disappear.