["Agribusiness, EarlyView. ", "\nABSTRACT\nA substantial share of U.S. soybean and corn exports from the Midwest moves by barge along the Mississippi River system to export terminals in the Louisiana Gulf. Transportation costs between Midwestern grain elevators and export terminals create a wedge between prices at these locations, and shocks to these costs are partially passed on to farmers through lower cash bids and weaker basis. We estimate the pass‐through rate of river transportation cost shocks to farmers using elevator‐level cash bids and barge freight rates in a fixed‐effects instrumental variables model, with river levels serving as an instrument. We also examine interaction effects for distance to a river port, distance to a processing plant, and the density of nearby elevators. Results indicate that higher river transportation costs weaken soybean and corn basis. The negative effect is smaller for elevators located farther from a river port or in areas with more nearby elevators, while distance to a processing plant plays a limited role in mitigating barge rates being passed through to basis. Pass‐through for corn is more strongly moderated by local elevator density, whereas pass‐through for soybeans is more sensitive to distance from a river port. These findings help farmers assess their exposure to basis risk from river transportation disruptions. Our results also provide policymakers with an empirical measure of the cost of such disruptions on farmers, informing the valuation of infrastructure investments that mitigate them.\n"]