Archaeologists commonly use the onset of the construction of large burial monuments as a materialindicator of a fundamental shift in authority in prehistoric human societies during the Holocene. High-quality direct evidence of this transition is rare. We report new interdisciplinary research at thearchaeological site of Nan Madol that allows us to specify where and when people began to constructmonumental architecture in the remote islands of the Pacific. Nan Madol is an ancient administrative andmortuary center and the former capital of the island of Pohnpei. It was constructed over 83 ha of lagoonwith artificial islets and other architecture built using columnar basalt and coral. We employedgeochemical sourcing of basalt used as architectural stone and high-precision uranium-thorium seriesdates (230Th/U) on coral from the tomb of thefirst chief of the entire island to identify the beginning ofmonument building at Nan Madol in AD 1180e1200. Over the next several centuries (AD 1300e1600)monument building began on other islands across Oceania. Future research should be aimed at resolvingthe causes of these social transformations through higher quality data on monument building.