This article analyzes the integration of the Spanish money market in the nineteenth century. We use a Band-Threshold Autoregression model of prices of bills-of-exchange in ten cities to measure market convergence and efficiency in 1825-1875. While price gaps generally decreased during the period, progress in efficiency was limited to a small group of cities. We suggest that convergence was associated to the reduction in transaction costs, which started well before the railways through improvements in roads and postal services. By contrast, the heterogeneous behavior of efficiency might be associated to economic geography changes and their effects on monetary leadership.