This dissertation treats the seals and seal impressions found during the 1985 and 1987 excavations of the Eastern Lower Town Palace at Tell Leilan (ancient Šeḫna/Šubat-Enlil) in Syria. The dataset comprises a large quantity of clay tablets and sealings (or bullae) impressed with the seals of administrators working in the palace over a period of some 75 years, from the time of its initial construction in the early second millennium, when Tell Leilan served as the diplomatic capital of Šamši-Adad’s “Kingdom of Upper Mesopotamia” (ca. 1808 – 1776 BCE), through subsequent building levels occupied by a succession of local emulative dynasties, including the kings of “the land of Apum” (ca. 1755 – 1728 BCE). Part I offers visual and descriptive reconstructions of the seal designs used by these administrators, analyzes their iconography and semiotic potential, and organizes them into style groups associated with specific social networks and use patterns within the physical and institutional contexts of the palace. An integrative approach, considering the visual and inscriptional information of the seals, the contexts in which they were found, and textual information provided by the administrative tablets found alongside them, provides substantial insight into what was being stored where, and which administrators had authority to access or restrict these goods. The patterns that emerge also make it possible to infer how imagery was deployed across specific spheres of activity, and how it might have corresponded to socio-administrative hierarchies. Part II considers some of the social semiotics and identity-making processes underlying the seal designs found in the Eastern Lower Town Palace. The corpus consists largely of various iterations of a standardized motif used by Šamši-Adad’s officialdom. This motif, which depicts an idealized ruler derived from earlier visual prototypes, not only functioned to reproduce and diffuse the royal message across newly unified northern Mesopotamia, but also promoted the idea of a shared cultural (or at least political) identity. Following the collapse of the “Kingdom of Upper Mesopotamia,” its own cultural production became fodder for the construction of social memory used to validate the regimes governing the subsequent, smaller kingdom of Apum.