When considering the available sources for Islamic history between the seventh and eighth centuries CE, there are few which have greater importance than al-Balādhurī's (d. ca. 892 CE/279 AH) Kitāb Futūḥ al-Buldān (The Book of the Conquest of Lands). While the text and its author are recognized for their importance as a historical source for the early Islamic period, there has previously been no in-depth study of either. This dissertation works to correct these gaps in knowledge of the author and his text by investigating the construction, form, content, and early reception history of al-Balādhurī's book. This research begins by providing a manuscript tradition of Futūḥ al-Buldān, including a discussion of a previously unpublished manuscript. It thereafter illuminates the background of al-Balādhurī, bringing together much of the previous scholarship on the author while augmenting that information with an analysis of biographical sources and the text itself. It situates the author and his text in its ninth/third century milieu, a period of history where the early Arabic historical tradition was still in its infancy and only just being committed to writing. It suggests the text was likely completed at the end of the "anarchy at Sāmarrā'" in the late 860s CE, and highlights the author's role at the court of several 'Abbāsid Caliphs. After this, it discusses a number of al-Balādhurī's most important (and, in some cases, previously understudied) sources of information, and argues that the author chose to differentiate when he was learning information directly from a teacher and when he had access to written sources. It then analyzes the content and themes of the text, placing special attention on the unique form of Futūḥ al-Buldān and its importance in providing modern scholars with information on the conquest, settlement, and building projects of the early Islamic world. In considering these key themes, this research then argues that Futūḥ al-Buldān defies traditional modern genre classification by borrowing form and content from several different Arabic genres including conquest literature (futūḥ), legal texts, and administrative geographies. It contends that both the text's content and form suggest that it was written to be read by courtly administrators in the service of the state as both a site of memory (lieu de mémoire) and as an "administrator's handbook" during a time of upheaval in the 'Abbāsid realm. Finally, it considers the legacy of Futūḥ al-Buldān and the popularity of al-Balādhurī's book throughout the medieval period through an analysis of textual reuse.