Monthly mean discharges for the period of record are given for the streamflow-gaging stations along the upper Mississippi River from its headwaters to Prescott, Wisconsin, as well as for the first upstream streamflow-gaging station on the major tributaries of the Mississippi River, the Minnesota and St. Croix Rivers. Differences in the monthly mean discharge between selected upstream and downstream streamflow-gaging stations are given. The differences were calculated by subtracting the monthly mean discharge from the upstream streamflow-gaging station or stations from the downstream station. The difference is reported at the downstream streamflow-gaging station.