Abstract: In the 1st millennium CE, a region in what is now Zambia became home to diverse and slowly spreading communities of iron-using farmers; by the late 1st/early 2nd millennium CE, the area became encircled by large, emergent polities and spheres of influence, through which diverse goods, people, and ideas traveled. This paper brings together historical, ethnographic, metallurgical, archaeological, and geophysical data to reconstruct the work of craftspeople – particularly iron workers – over the longue durée in the Machile Valley, Western Zambia from the 8th-18th centuries. In doing so, I center the ways craftspeople effected, and were affected by, local and regional changes across southern Africa, and identify at least two periods when distinct communities of iron-working knowledge and practice co-existed within a stretch of the valley only c. 40km long. As changes in global and regional political economic systems intertwined with the increasing importance of kinship ties in village life and new conceptions of landscapes in the early 2nd millennium, craftspeople converted specialized knowledge into other symbols of status and prestige. Incorporation of oral and historical records explains dramatic increases in the scale and organization of production in Machile c.1600CE and shows how craftspeople were affected by the formation of the nearby Lozi state during the 16th-18th centuries. Archaeometallurgical and spatial comparisons of Machile iron smelting sites over the past thousand years suggest beliefs around secrecy and access to specialized knowledge fluctuated there, underscoring the historical specificity of the practices documented in 18th- 20th-century ethnographic texts. I show how frontier interactions in southern Africa are historical, dateable events rather than ahistorical abstractions, with discrete and localized archaeological traces.