Globalization, if defined as the integration of international commodity markets, started in the eighteenth century and progressed gradually and with some setbacks into the nineteenth century, instead of suddenly appearing at some point after the 1820s. We use grain prices in Europe and the Americas to determine the extent and dynamics of market integration throughout the eighteenth and nineteenth centuries. An innovative methodology, with special attention being paid to changes in residual dispersion of the univariate models of relative prices between markets, permits us to obtain a measure of market integration over time.