With growing material databases, researchers continue to highlight a combination of unique trajectories of change and variables that contributed to the emergence and development of social complexity. What kinds of variables contributed to these profound cultural changes? How did leaders and rulers emerge, consolidating political power over populations? How did these societies develop political institutions that resulted in novel forms of social organizations within respective areas? This chapter adds to ongoing scholarship and debates with a case study from Southeast Asia, examining a pathway to “state” formation in the Red River Valley of present-day northern Vietnam, also known as the Bac Bo region. Specifically, the ancient settlement known as Co Loa provides an interesting context of emergent complexity that was unprecedented in the RRV region, one that was shaped by both its geographic positioning as well as its interactions with societies of neighboring regions. In addition to local variables of social, economic, and political change, a prominent factor for the Co Loa phenomenon pertains to interactions with emergent Sinitic civilization to the north. The chapter highlights both local and extra-regional factors for social change that stimulated the formation of the Co Loa Polity during the third century BCE. In doing so, it provides an argument for a punctuated nature of state development.