Does democracy curb domestic political violence? To study this, we focus on the United Kingdom’s Representation of the People Act of 1867—which is a critical juncture in the history of democratisation. Constructing a novel borough (‘urban centre’) level dataset on social conflict events and economic performance around the 1868 elections (the first elections where newly enfranchised citizens could vote), we exploit arguably exogenous variation in enfranchisement intensity. We find a strong and robust peace-promoting effect of franchise extension and identify as a major channel of transmission the increase of the population’s political influence (voice) and local economic growth.