Back in 2010, I visited a labor camp that houses some of the migrant workers who grow America's fruit and vegetables. I found people living densely in shanty-like structures made of scrap metal and cinder block, surrounded by vast fields and long rows of greenhouses. Strangers in a strange land who didn't speak the language, hundreds of miles from home, they lived at the mercy of labor contractors who, they claimed, made false promises and paid rock-bottom wages. Like all Big Ag-dominated areas, the place had a feeling of desolation: all monocropped fields, mostly devoid of people, and lots of billboards hawking the products of agrichemical giants Monsanto and Syngenta.

You might think I had made my way to Florida's infamous tomato fields, or somewhere in the depths of the California's migrant-dependent Central Valley. Those places remain obscure to most Americans, but the gross human exploitation they represent has at least been documented in a spate of excellent recent books, like Barry Estabrook's Tomatoland, Tracy McMillan's The American Way of Eating, and Seth Holmes Fresh Fruit, Broken Bodies. But I was somewhere yet more remote and less well-known: Sinaloa, a largely rural state in Mexico's northwestern hinterland.

If most Americans have heard of Sinaloa at all, it's because of the state's well-earned reputation as a center of Mexico's bloody drug trade. But in addition to the eponymous drug cartel, Sinaloa also houses vast-scale, export-oriented agriculture: farms that churn out the tomatoes, melons, peppers, and other fresh produce that help fill US supermarket shelves. And the people who do the planting, tending, and harvesting tend to be from the indigenous regions of Mexico's southern states, Oaxaca and Chiapas, where smallholder farming has been ground down by decades of free-trade policies pursued by the Mexican government, which left millions in search of gainful work to the north.