This paper is a study of the British conceptualization of Iraq as a geographic and socio-political territory upon the foundation of the British Mandate for Mesopotamia in 1920-1. The purpose is to trace the development of institutional knowledge about Iraqi geography, history, and ethnic and religious distribution back from the moment of inception. This paper asks two questions: what did officials in the Colonial Office, Foreign Office, and military think Iraq was, or should be, at the moment Britain took responsibility for turning Iraq into a sovereign nation-state, and what effect did this have on Iraq's geography and border formation? I show that the British imagined Iraq as a nation-state based around the rural and urban centers within the irrigated zone of the Shatt al-Arab, Tigris River, and lower Euphrates River, or “Mesopotamia.” This relatively densely populated riparian zone of agricultural and trade-based economies (also the site of the region’s Ottoman administrative centers, and the shrine cities of Najaf and Karbala) was documented on maps and in travel narratives as the home to the biblical Eden and the ruins of Islam’s Abbasid golden age, and which was now divided between a desert “wilderness” and settled “civilization.” This exoticized, text-based land of Mesopotamia was assimilated into the texts, maps, and institutional knowledge of British military planners and civil administrators engaged in the invasion and occupation of Basra, Baghdad, and Mosul provinces during World War I, and thence to the blueprints for the future Iraqi state. The source materials are travel guides, geographies and maps by independent scholars, surveying contractors hired by the Ottoman government like William Willcocks, and of course, British colonial and military officials such as Gertrude Bell and A. T. Wilson. All were involved in the invasion and occupation of the Ottoman provinces of Basra, Baghdad, and Mosul between 1914 and 1918, and all were frequent contributors to my other important source for this project, The Geographical Journal (London, 1893-). As the official record of The Royal Geographical Society, the Journal acted as a government-backed scientific journal and a forum for debate and inquiry into the geo-political issues facing the British Empire. My paper thus provides the first study of the Journal as a literary space for the overlapping, reciprocal relationship between knowledge of the “Orient” and imperial rule.