Over the past 10 years, the Missouri River has experienced a large downward shift in its stage discharge relationship at the Sioux City, Iowa, gaging station. The stage for a given discharge, in the range of 10,000 to 40,000 cfs, has decreased 5-8 feet in this time. A study of related data shows that the combined interaction of geologic, hydrologic, geometric, and hydraulic factors influenced this change. The major changes which combined to cause a general degradation in the river reach near Sioux City include a reduction in suspended sediment load, a shortening of the river channel in the area, construction of river training works, and a recent (7 year) increase in the mean yearly flows as well as increased peak flows. The resulting degradation and increase in total channel area below the high bank elevation have lowered the stage for a given discharge at Sioux City. This study illustrates the changes which have occurred in the river since 1950.