Maximum floodflows (stream discharges) that are known to have occurred on Mississippi streams were compiled. Most data were collected and archived by the U.S. Geological Survey in cooperation with Federal, State, and local agencies; however, some data were collected and provided by the U.S. Army Corps of Engineers. Maximum known discharges are plotted with drainage area and compared to an envelope curve derived from maximum known discharges at sites throughout the conterminous United States. This paper presents the maximum flood known to have occurred at a given gaged site, where stage and discharge measurements were obtained to determine the peak discharge, or at an ungaged site, where a flood was thought to be significant enough that an indirect measurement was computed to estimate the peak discharge.