This dissertation investigates the history of the development of Lebanon's Litani river between 1931 and 1965. I draw upon newly-available primary sources to examine the research, design, and construction of hydroelectric and irrigation infrastructure that connected the Litani and the rural Biqa' valley with Beirut. The Litani project was Lebanon's first grand-scale development scheme, central to America's technical aid strategy in the Middle East, and funded by a massive World Bank loan that burdened the country for decades. By focusing on collaboration and competition between a rising class of Lebanese engineer-technocrats and US experts, this dissertation reveals how competing designs for the Litani related to competing visions of development. The designs that prevailed corresponded to the World Bank's objectives rather than those of Lebanese engineers. However, the development project was not a monolithic imposition by the World Bank and Lebanese state onto a passive Lebanese people and landscape. Rather, it was a negotiated and contingent process, a means for Lebanese engineers to assert their national leadership and for rural communities to challenge the state. Communists, religious leaders, and businessmen debated the project with engineers and politicians in the burgeoning press. These debates contested the nature of the Lebanese state and its relationship to the United States. Ultimately, the Litani project drew water away from rural cultivators and channeled electrical outputs exclusively to Beirut, reinforcing a cartography of unequal development that privileged the capital. This inequality simultaneously provided a basis for rural communities to mobilize into larger political-religious formations and make claims on the state. By putting the Litani at the center of its historical narrative, this dissertation reexamines the history of modern Lebanon, international development, and interrelations between technology, society, and environment.