This chapter centres on territories, the first of this book’s three fields of interest, and exposes the history of territorialityTerritoriality for the gangs and factionsFaction operating in Rio in the period under study. It does so by introducing ‘jailside’ and ‘hillside’—the two critical habitats for these urban armed groups. The chapter then proceeds with a historical reconstruction of the trajectory of Rio's factions, from their emergence in the 1970s to their internal conflicts in the 1980s and their eventual splintering and degradation in the 1990s and 2000s. The chapter thus demonstrates that faction reliance on both types of critical habitats was a key maladaptation that, despite providing larger revenue, led to internal fragmentation and significant weakening in the face of multiple selection pressures.