Helmand Province is the toughest place in Afghanistan, full of drug lords, smugglers and the insurgent Taliban. That's why the US Agency for International Development is there—building its fifth largest project in the entire world. USAID is developing Helmand Province as if it were a country. The centerpiece is a hydroelectric project called the Kajaki Dam. The US will invest some $500 million to restore the dam, but for the moment nearby villages are empty and access roads have been cut off by the Taliban. Carlotta Gall reports from Afghanistan for the New York Times.