Immigrants from an obscure corner of Mexico are changing heroin use in many parts of America. Farm boys from a tiny county that once depended on sugar cane have perfected an ingenious business model for selling a semi-processed form of Mexican heroin known as black tar. Using convenient delivery by car and aggressive marketing, they have moved into cities and small towns across the United States, often creating demand for heroin where there was little or none. In many of those places, authorities report increases in overdoses and deaths.
