A border fence separates Nogales, Arizona, and Nogales, Mexico.

After crossing the Sonoran Desert of Arizona, migrants often rendezvous with a smuggler who will drive them to Tucson or Phoenix. People are told to leave behind any evidence of migration, including soiled clothes, first aid equipment, water bottles, and backpacks. The Undocumented Migration Project has labelled these modern archaeological sites Migrant Stations; and has recorded hundreds since 2009. This migrant station is just north of the Arizona town of Arivaca, approximately a four-day walk from the border.

Mobile infrared camera systems plug leaky points along the U.S./Mexican border in Arizona.

Migrants left these personal effects behind in the Sonoran Desert of Arizona.

Baboquivari Peak, in the distance, is a sacred mountain for the Tohono O'odham people of northern Mexico and southern Arizona—and one of the few easily recognisable landmarks for migrants, who typically cross the desert with no map, compass, or GPS to guide them. As long as the mountain is to their left, they know they’re walking north.