Chapter 1 presents a social history of the great exodus. It argues that in late-1940s and early-1950s Taiwan, the influx of civil war refugees from China produced two forms of social dislocation or “social trauma” – one experienced by the mainland refugees themselves; the other experienced by the native Taiwanese population who resided in the island’s major cities. The mainlander social trauma is illustrated by both personal testimonies given decades later at the present time and historical evidence: population census, archival social data, and newspapers. The Taiwanese dislocation due to the social upheaval generated by the incursion of a large number of dispossessed mainlanders is not remembered collectively nowadays. It is nonetheless revealed by the same sets of documentary evidence that illustrate mainlander displacement. By highlighting the discrepancy between what is remembered and what is forgotten in today’s Taiwan with regard to the great exodus, the chapter illuminates the difference between history and memory. It underlines the methodological point of the book: scholars need to conduct historical research to put contemporary memories in perspective.