Claims to exceptionalism notwithstanding, the history and contemporary expression of North America are overwhelmingly transnational, drawing on—as well as acting upon—peoples and resources stretching from the Atlantic and, increasingly, from the Pacific. This chapter primarily follows the expansion of the United States, by far the most powerful North American country, from its Atlantic origins through its ongoing westward march towards the Pacific Basin. Despite the continued power of Atlantic-centered views in North American imaginations, this chapter shows how the US emerged as a Pacific power.