Mexico’s southern border bends east and northeast, from the Pacific at one end to the Caribbean at the other, much of it tracing the bottom of the big Mexican state of Chiapas. The city of Tapachula remains one of the principal gateways for Central American migrants; for many years this city was the southern terminus of the freight train that rumbles north toward the U.S. border, with migrants clinging to the roofs and sides. They call the train la bestia, the beast, and it is the subject of grim warnings about the importance of staying awake on the roofs of the rolling cars, lest one lose one’s grip and fall to dismemberment or death. There is a celebrated recuperation facility in Tapachula, run on donations, that takes in migrant amputees who have fallen from the freight trains and lost arms or legs beneath the metal wheels.

Tapachula is a city of 270,000 whose commercial streets and big central plaza crowd late into the night with taxis, motorcycles, delivery trucks, colectivo jitneys, businessmen on cell phones, teenage girls in tight blue jeans, Maya women in woven skirts, boys selling DVDs, children selling candy, and women slicing chili-powder-sprinkled mango and papaya into small plastic bags. Immigrants helped build the city’s economy—coffee merchant and hotelier Tomás Edelmann Blass inherited his German great-grandfather’s plantation north of town; orthopedist José Mak Chong is a second-generation Chinese Mexican—and when they talk now about undocumented migrants in their midst, they sound like Americans: resentful, sympathetic, patronizing, perplexed. A Mexican shop owner in Tapachula described the trouble with the Central Americans in town: The Guatemalans are too servile, he said, the Hondurans too gang-inclined, the Salvadorans too hotheaded. And all of them—simply because they’re isolated, vulnerable, and likely to be carrying money—attract assailants whose toxic presence alarms everybody in town. “I suppose I’d hire a Guatemalan over a Honduran, and a Honduran over a Salvadoran,” the shop owner said. “These people aren’t interested in staying in Mexico anyway. Those dollars are pulling them north.”

In Chiapas, where coffee, banana, and mango harvests have depended for decades on Guatemalan agricultural workers, employers underpay undocumented workers or refuse to pay them at all, counting on them to fear repatriation too much to complain. Gang members as well as freelance toughs lurk along the riverbanks and footpaths, alert to the backpack-carrying travelers who may have money secreted away. Although certain villages along the freight train routes are known for locals who hand free food up to the migrants hanging off the railroad cars, the locals at other stops jump onto the cars to beat and rob migrants, sometimes with police watching or joining in.