This article investigates the role of colonial pressure on state centralization and its relationship to subsequent development by analyzing the influence of Western colonial threats on Siam’s internal political reform. Unlike other countries in the region, Siam remained independent by adopting geographical administrative boundaries and incorporating its traditional governance structures into a new, centralized governance system. The authors find that the order in which areas were integrated into the centralized system depended on the interaction between precentralization political structures and proximity to British and French territorial claims. The authors show that areas centralized early in the process had higher levels of infrastructure investment and public goods provision at the time the centralization process was completed in 1915 than those centralized later in the process. They also show that early centralization during the Western colonial era continued to be strongly associated with higher levels of public goods provision and economic development, and that this relationship persists today.