SHANGHAI—Henry Luce, the founder of Time magazine, was raised in China as the son of a Presbyterian missionary.

He and his family were among a population of foreigners that swelled to as many as half a million before 1949. Some were teachers, doctors and journalists. Others were merchants, engineers, architects and bankers. Within a few years of the Communist takeover almost all had fled or been kicked out. Mao harbored such loathing for Shanghai, China’s most cosmopolitan city, that he considered emptying it out completely...