KEARNY, New Jersey It is the deadliest target in a swath of industrial northern New Jersey that terrorism experts call the most dangerous two miles in America: a chemical plant that processes chlorine gas, so close to Manhattan that the Empire State Building seems to rise up behind its storage tanks. According to U.S. Environmental Protection Agency records, the plant poses a potentially lethal threat to 12 million people who live within a 14-mile, of 22-kilometer, radius. Yet on a recent Friday afternoon, it remained loosely guarded and accessible. Dozens of trucks and cars drove by within 100 feet, or...