The historical-spatial transformation of Iranian cities has primarily been conceptualized through case studies of well-known metropolises and major administrative centers. Conversely, the complex mechanisms of change in mid-sized cities with long historical backgrounds have rarely been systematically investigated. The city of Bijar, as a significant settlement hub in the strategic region between the Zagros Mountains and the Iranian Central Plateau, serves as an illustrative example for addressing this research gap. The primary objective of this study is to precisely elucidate the process of Bijar’s historical-spatial transformation from the earliest archaeological settlement evidence to the end of the Pahlavi era, and to provide a critical analysis of the factors influencing the formation, consolidation, and evolution of its spatial structure. This research employs a descriptive-analytical and historical approach. Data were gathered through a synthesis of archaeological sources, primary historical texts, archival documents, historical maps, and rigorous field surveys. Analysis was conducted within an integrated theoretical framework encompassing landscape archaeology, urban archaeology, and the modern “Historic Urban Landscape” (HUL) approach to comprehensively explain the role of environmental, political, economic, and cultural factors in the city’s structural evolution. Findings demonstrate that during the initial formation stages, ecological characteristics and the strategic regional position were the primary drivers of settlement. From the Islamic period, particularly the Safavid and Qajar eras, the concentration of political power, religious institution development, expansion of endowments (vaqf), and regional commercial prosperity led to the consolidation of the historical core. During the Pahlavi era, top-down modernization programs and infrastructure development transformed parts of the spatial structure. Based on comparative analysis, this study concludes that Bijar’s transformation results from a dynamic interaction between environmental, political, and economic factors. It proposes an interpretive model where urban change is not the product of a single dominant factor, but the result of the gradual and continuous shift in the relative weight of these variables over time.