The archaeological cultures of the Korean peninsula provide numerous case studies of the formation, structure, and function of ancient complex societies and states. In southwestern Korea, the Mahan (ca. 50 b.c.e.–c.e. 475) occupied a large region marked by similarities in material culture, but decentralized politically. The Paekche kingdom (ca. c.e. 250–660) had its origins as a Mahan polity in the Han River valley, later centralizing its authority and expanding its territory. This article discusses two sites: the Paekche capital of P'ungnap T'osŏng in modern Seoul and a large Mahan town recently excavated in Chŏlla Province known as Kwangju Palsan. The political economy and social structure of each site is investigated using ceramic remains, artifacts that played a large role in daily life across classes and in the elaboration of elite culture. With high-resolution chemical data from Instrumental Neutron Activation Analysis (INAA) on potsherds, specific production signatures can be identified for each site. This allows comparison of the proportion of locally produced and imported pottery at each site and even reveals when P'ungnap T'osŏng and Kwangju Palsan exchanged ceramic goods. These patterns reveal similarities and differences in Mahan and Paekche political economies, ultimately illuminating the Mahan roots of Paekche social organization.