A new trend has been emerging in China’s urban and regional politics, as it is becoming prevalent to extend one municipal authority to another, transcending boundaries, often through the establishment of joint development zones. These newly produced subnational territories are worth further attention to clarify the underlying political dynamics of China’s changing state space. This paper examines the Shenzhen–Shanwei Special Cooperation Zone in Guangdong and analyses the political–spatial processes through which a certain area of Shanwei has been transformed into the ‘Eastern frontier of Shenzhen’. Looking into the relational power nexus that has also been inflected by trans-scalar and cross-boundary dynamics, as well as its manifestations in urban landscapes, we propose extended local territory as a key analytical concept to explore how and how far the rise of extensive territoriality has been articulated with intensive localities. Empirically, we elaborate on the ways in which the territorial ambition and authority of Shenzhen have been managing to traverse boundaries, while also recognising that Shenzhen’s aspiration of materialising its extensive territoriality is challenged by both scalar constraints and the grassroots politics rooted in local history and geography. Addressing the dialectics between the extensive territoriality and intensive locality, we attend to the inter-topological effects and trace the patterns of correlation that are involved in this process, which also turns out to be a critical approach to better understanding changing state spaces in and beyond China.