This paper estimates structural demands for grain transportation on the upper Mississippi and Illinois Rivers. Grain is the predominant commodity transported on these waterways. Analysis indicates Seemingly Unrelated Regression (SUR) to be a superior method for estimating each waterway’s structural demand. Results show rates, foreign and domestic demands, floods, season, and river water level influence demands. Further, the analysis suggests that a detailed analysis of river freight demand is a necessary precursor of a defendable study into the economic feasibility of improving transportation infrastructure on the upper Mississippi and Illinois Rivers.