What is the legacy of Japanese colonial rule in East Asia? In this article, I use a geographic regression discontinuity design to examine of the long-run effects of Japanese rule over northern China. I find that the Japanese colonization of northern China had a positive long-run effect on state institutions—with persistent increases in schooling, health, and bureaucratic density. I also find suggestive evidence that colonization led to increases in wealth, as measured by census data and nighttime luminosity. The positive legacy of Japanese colonization in northern China suggests that intense state building efforts can pay long-run dividends, even in the context of a brutal and extractive regime.