The authors provide, for the first time, an estimate of the real gross domestic product of Switzerland between 1914 and 1947. The estimate is obtained from published data on three other measures of Swiss economic activity during this period: net national product, industrial production, and the transport volume of Swiss railroads. These underlying series closely represent the economic growth of Switzerland; but, they also seem unreasonably volatile as proxy measures of total production, and hence, are filtered by moving averages. Although such smoothing might reduce the accuracy of the estimates, comparisons to U.S. data suggest any such loss is small.