What effect did trade have on the size distribution of firms during the first wave of globalization? Three historical datasets from the German Empire between 1875 and 1907 were collected and harmonized to answer this question. This paper combines industry census and bilateral railway trade data from the same industry and region along with industry-level tariff data. The evidence shows that increases in aggregate trade caused the share of firms to shift from smaller to larger firms. Exogenous decreases in tariffs caused an increase in the share of the largest firms. The regional distributive effects of trade on inequality between firms that are discussed in the contemporaneous literature were already present during the first wave globalization.