Project Safe Neighborhoods (PSN) is a federally funded initiative that brings together federal, state, and local law enforcement to reduce gun violence in urban centers. In Chicago, PSN implemented supply-side gun policing tactics, enhanced federal prosecution of gun crimes, and notification forums warning offenders of PSN’s heightened criminal sanctions. Prior evaluations provide evidence that PSN initiatives have reduced crime in the first few years of their operation. But over a decade after the program was established, we still know little about whether these effects are sustained over an extended period of time. This Article examines PSN Chicago, an anti-violence program in operation since 2002. Consistent with a previous evaluation, we find that several program components were associated with reductions in violence in the initial target areas. These associations, however, are concentrated in the first few years of the intervention. We also examine the effect of PSN in several subsequent expansion areas and find no detectable effects. We suggest that the effects of PSN were diluted as the program expanded to larger areas of the city without an increase in funding or resources. Still, we recommend that future research consider PSN’s strategies in Chicago that appeared effective in the early years and leverage those insights for future programs.