In the 1990s, the city of Hoeryong, North Korea, bore testament to the privations of life under the country's Stalinist regime. Untold numbers of locals starved to death during a famine that may have killed some 2 million or more nationwide. But the outlook has brightened considerably for the estimated 100,000 residents, due to the arrival of a force the North Korean government has spent almost 60 years trying to keep out: capitalism.
According to interviews with refugees in South Korea and more than a dozen people who routinely slip between China and North Korea, Hoeryong, which is located on the...