Heroin that lands here via Mexican drug-trafficking organizations is largely sent through legal entry points, according to a 2017 DEA report on the country’s drug supply. Drugs are hidden in secret compartments in passenger vehicles, or secreted among legitimate goods in tractor-trailers. To a lesser extent, Mexican trafficking organizations do send individual smugglers and scouts across remote areas along the border. But sending drugs through legal border crossings is more bang for a trafficker’s buck -- it allows for the shipment of far larger quantities than could be driven across rough terrain.