We assess the impact of access to Bangkok’s nineteenth-century canal network on orchard productivity using a new dataset constructed from 1880s orchard land deeds. We find that properties located adjacent to canals, which were built for purposes exogenous to orchard production, had significantly higher labor productivity than those located inland. Gaining direct access to canals led to productivity improvements through better access to markets, which in turn enhanced cultivators’ welfare. We conclude, based on a method developed by Oster (2019), that unobserved selection bias is negligible, allowing for the positive impact of canal access to be interpreted as causal.