The 1850s and 1860s were a crucial era in the history of East Asia. The opening of treaty ports and advances in information and navigational technologies both generated new commercial opportunities and brought more people and commodities from Europe and America to East Asia. What were the consequences of these political and socioeconomic changes and the resultant spatial interconnections? I argue that spatial interconnections rendered centuries-old nonstate spaces in East Asia increasingly problematic, to the extent of creating international conflicts. To illustrate this, I reconstruct the mutual influence among places constructed by and shown in the lives of the shipwrecked American vessel Rover and its crew in East Asian waters. Their activities embodied how transpacific and East Asian communication and commerce, and the growing treaty port community in China, became entangled with how Taiwanese aborigines managed their interaction with the outside world. In this and similar borderland incidents, spatial interconnections between central and peripheral East Asia constructed by ordinary people crossing borders, and the problems arising from such interactions, led to the problematization of peripheries in the 1860s.