"Jusionyte explores the sister towns bisected by the border from many angles in this illuminating and poignant exploration of a place and situation that are little discussed yet have significant implications for larger political discourse."—Publishers Weekly, STARRED Review''From MacArthur "Genius" Fellow Ieva Jusionyte, a gripping ethnography of firefighters and paramedics on the US–Mexico border, caught between state power and the ethics of rescue.Emergency responders on the US-Mexico border operate at the edges of two states. They rush patients to hospitals across country lines, tend to the broken bones of migrants who jump over the wall, and put out fires that know no national boundaries. Paramedics and firefighters on both sides of the border are tasked with saving lives and preventing disasters in the harsh terrain at the center of divisive national debates.  Ieva Jusionyte’s firsthand experience as an emergency responder provides the background for her gripping examination of the politics of injury and rescue in the militarized region surrounding the US-Mexico border. Operating in this area, firefighters and paramedics are torn between their mandate as frontline state actors and their responsibility as professional rescuers, between the limits of law and pull of ethics. From this vantage they witness what unfolds when territorial sovereignty, tactical infrastructure, and the natural environment collide. Jusionyte reveals the binational brotherhood that forms in this crucible to stand in the way of catastrophe. Through beautiful ethnography and a uniquely personal perspective, Threshold provides a new way to understand politicized issues ranging from border security and undocumented migration to public access to healthcare today.