This chapter traces the history of American presence in Southeast Asia. The American legacy in the region began with traders and missionaries during the first half of the nineteenth century, then progressed to diplomats and official relations during the second half, and then to the arrival of American armed forces at the turn of the twentieth century. Meanwhile, America’s commercial interests and footprint continually broadened and deepened; educational and religious ties also blossomed. Except in the Philippines, America was largely seen as a benevolent partner—but not yet a power. That would change in the wake of World War II and the Cold War. With the advent of communist regimes in China, North Vietnam, and North Korea, and the ensuing Korean War, Southeast Asia took on a completely different cast in Washington. It became one of two major global theaters of conflict against communism. Thus began America’s long and draining involvement in Vietnam and Indochina (1958–1975). But with the end of the long and exhausting Indochina conflict, which tore the United States itself apart, American attention naturally began to wane and dissipate. Yet, the United States continued to engage and build its relations with the region from the Carter through the Bush 43 administrations.