The border between Nogales, Arizona in the U.S. and Nogales, Sonora in Mexico used to be a pretty relaxed.
"Floats went down the street and into Nogales, Arizona. A coronation was held on a platform on la linea, and the Fiesta de Mayo Queen was crowned. Both towns celebrated," Nicolas Demetrio Kyriakis told author Paul Theroux for The New York Times. Americans, notably servicemen from nearby U.S. Army Fort Huachuca, would cross over for Mexican goods or just a taste of the local food.
After 9/11, soldiers from the fort stopped visiting and border patrol started asking for passports. Meanwhile, violence related to drug cartels ramped up - though things have reportedly improved recently following heavy investment in security on the Mexican side.
Whatever happens next, it is clear how inextricably linked these two cities will always be, as is clear in a stunning photograph by David Rochkind from his book Heavy Hands, Sunken Spirit: Mexico at War:
David Rochkind