Abstract: This study exploits the changes in agricultural productivity brought about by the introduction of potatoes to the Old World from the New World, and provides an estimate of the impact of agricultural productivity on population growth and economic development. Using a difference-in-differences estimation strategy, we examine whether countries with a greater geographic suitability for the adoption of potatoes witness a larger increase in population and urbanization growth after potatoes were introduced to the OldWorld. According to our most conservative estimates, the adoption of potatoes explains 18% of the observed post-1700 increase in population growth and 37% of the increase in urbanization growth. We show that our results are robust to a wide range of alternative determinants of population growth and economic development during this period, including lobalization, colonial rule, and the slave trade.