China’s land reform in 1978–84 unleashed rapid growth in farm output and household income. In new data on reform timing in 914 counties, we find an immediate trend break in the fraction of male children following the reform. Among second births that followed a firstborn girl, sex ratios increased from 1.1 to 1.3 boys per girl in the 4 years following reform. Larger increases are found among families with more education. The land reform estimate is robust to controlling for the county-level rollout of the One Child Policy. Overall, we estimate land reform accounted for about 1 million missing girls.