This dissertation charts the evolution of what I call American commercial maritime imperialism, a process pursued by American merchants and U.S. officials working to control sailor populations and American property overseas—far beyond the national borders of the United States. Between 1787 and 1848, the United States expanded its sovereignty from the east coast of North America westward to the ports and corridors of the Pacific Ocean. As American merchants and U.S. officials worked to create an infrastructure of authority and control over strategically important spaces in the Pacific, a maritime working population labored and resisted the terms of their service aboard vessels and ashore at ports of trade. By employing a multi-local approach to examine five commercial nodes of American imperialism in the Columbia River region, the Chile-Peru coast, the Hawaiian Islands, the Pearl River Delta, and the California waterfront, this dissertation demonstrates how obstructions to American global trade prompted the United States to establish and expand new and dynamic forms of sovereignty in the Pacific. It considers how the commercial activities of American merchants, their crews, and U.S. officials shaped the contours of early American state formation, economic growth, and foreign diplomacy. This approach to American imperial expansion represents a break from much of the scholarship on the subject. Studies of American Empire during the first half of the nineteenth century generally focus on westward migration, forced labor, and military conflict in northern Mexico and on what became the southwestern part of the United States. Histories of American foreign diplomacy overseas typically focus on the Spanish American War (1898) when the nation seized islands across the Pacific and in the Caribbean. By examining developments in the commercial maritime history of early America, this dissertation creates a global history of the United States. With its focus on maritime workers and merchant investors, this study contributes to new histories of U.S. political economy, global capitalism, and antebellum American foreign diplomacy.