By shifting from the military to the legal and economic aspects of this history, it can enrich our understanding of Washington’s maritime policy in Cold War East Asia. Thus, this chapter sketches out the interaction between the United States and its local partners in maritime East Asia, including Japan, South Korea, and Taiwan, from a non-military perspective. These local partners were sheltered under the military umbrella of its system of hub-and-spoke alliances formed by mutual defence treaties. However, between them, the historical twists and turns of sovereignty rendered the international politics of East Asia all but impenetrable. Because these countries are linked by the maritime space, a consideration of the demarcation of internationally accepted maritime boundaries and fishing zones, a matter bound up in issues of sovereignty and local interests that remained controversial over the course of two centuries, provides us with a historical lens through which to examine the political calculations of each American ally in maritime East Asia and how these influenced Washington’s deliberations as it designed its global maritime policies.