The widespread presence of criminal organizations in strong states presents a theoretical and empirical puzzle. How do criminal organizations — widely believed to thrive in weak states — expand to states with strong capacity? I argue that criminal groups expand where they can strike agreements with local actors for the provision of illegal resources they control, and that this practice is particularly profitable in strong states where costs from prosecution are higher. Using a novel measure of organized crime presence, I show that (1) increases in demand for unskilled labor — and in criminals’ capacity to fill it by exploiting migrants — allowed southern Italian mafias to expand to the north, and that (2) mafia expansion gave a persistent electoral advantage to political parties collaborating with them. This suggests the need to reconceptualize criminal organizations not only as substitutes for weak states but as complements to strong states.