This chapter investigates internal frontiers, that is, spaces not 
controlled by the state directly, or administered indirectly through 
native officials. It examines why the Ming state failed to control the 
internal frontier of Iron Chain Gorge, a conglomeration of autonomous 
upland ethnic communities in western Yunnan, for almost 200 years. 
Focusing on the agency of these upland communities in maintaining their 
own autonomy, the author clarifies the nature of political organisation 
within the internal frontier, and shows how fierce opposition by upland 
leaders limited Ming control of surrounding lowland areas until the 
conquest of Iron Chain Gorge in 1574. The survival of an internal 
frontier compelled Ming bureaucrats to heavily rely on co-administration
 with hereditary native officials. Co-administration was not simply a 
product of the uneven coming together of regular bureaucrats and 
hereditary native officials, but can be interpreted as the Ming state’s 
recognition of the limited extent of their governance. The author 
concludes that this administrative infrastructure prolonged the 
existence of the Iron Chain Gorge internal frontier, and that it 
restricted the reach of social reconstruction. The concept of internal 
frontiers is reviewed in the context of James Scott’s Zomia, and the 
implications it has for the history of Southwest China are discussed.