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Fremling, C. R. and T. O. Claflin (1984). Ecological history of the Upper Mississippi River. Pages 17-18 in J. G. Weiner, R. V. Anderson and D. R. McConville, eds. Contaminants in the Upper Mississippi River: Proceedings of the 15th Annual Meeting of the Mississippi River Research Consortium, La Crosse, Wisconsin (USA), Mississippi River Research Consortium.

The Upper Mississippi Valley, opened to Caucasians by Joliet 's explorations in 1673, was the site of rapid population growth and trading during the 1700's. This section of the river was surveyed in the early 19th century. The beginning of steamboat travel in 1823 led to navigation improvements by the Army Corps of Engineers starting in 1824. Settlements continued to grow in number and population, stimulating cutting of forests for lumber and agricultural activities, particularly steepland farming. These practices contributed to erosion and degradation of the river system. The Rivers and Harbors Acts of 1878, 1890, and 1907 resulted in channel deepening and other construction works in the section from Minneapolis to the Ohio River. These works used wing and closing dams, shore protection, and auxiliary dredging, permitting open-channel navigation. By 1870 the fisheries were rapidly declining as a result of wide fluctuations in water level which stranded fish in backwaters. Fish rescue operations were begun in 1879 and continued until the 1950 's in a few locations. In the 1930 's more extensive channelization projects started. The channel was deepened to 9 ft by construction of locks and dams (29 built during this period), supplemented by dredging. As a result of the impoundments, the river habitat has changed, vastly increasing the marsh area and slack water area habitat available for invertebrates, periphyton, fish (139 species), furbearers, and waterfowl. Some long-term detrimental changes caused by the channel modifications include accelerated sedimentation (changing wetlands into floodplains), eutrophication, and accumulation of industrial wastes.