<P> Since the beginning of the 20th century, the Missouri River has been extensively engineered for water transport purposes, and about 32 percent of the river now flows through artificially straightened channels . In 1912, the USACE was authorized to maintain the Missouri to a depth of six feet (1.8 m) from the Port of Kansas City to the mouth, a distance of 368 miles (592 km). This was accomplished by constructing levees and wing dams to direct the river's flow into a straight, narrow channel and prevent sedimentation . In 1925, the USACE began a project to widen the river's navigation channel to 200 feet (61 m); two years later, they began dredging a deep - water channel from Kansas City to Sioux City . These modifications have reduced the river's length from some 2,540 miles (4,090 km) in the late 19th century to 2,341 miles (3,767 km) in the present day . </P> <P> Construction of dams on the Missouri under the Pick - Sloan Plan in the mid-twentieth century was the final step in aiding navigation . The large reservoirs of the Mainstem System help provide a dependable flow to maintain the navigation channel year - round, and are capable of halting most of the river's annual freshets . However, high and low water cycles of the Missouri--notably the protracted early - 21st - century drought in the Missouri River basin and historic floods in 1993 and 2011--are difficult for even the massive Mainstem System reservoirs to control . </P> <P> In 1945, the USACE began the Missouri River Bank Stabilization and Navigation Project, which would permanently increase the river's navigation channel to a width of 300 feet (91 m) and a depth of nine feet (2.7 m). During work that continues to this day, the 735 - mile (1,183 km) navigation channel from Sioux City to St. Louis has been controlled by building rock dikes to direct the river's flow and scour out sediments, sealing and cutting off meanders and side channels, and dredging the riverbed . However, the Missouri has often resisted the efforts of the USACE to control its depth . In 2006, several U.S. Coast Guard boats ran aground in the Missouri River because the navigation channel had been severely silted . The USACE was blamed for failing to maintain the channel to the minimum depth . </P> <P> In 1929, the Missouri River Navigation Commission estimated the total amount of goods shipped on the river annually at 15 million tons (13.6 million metric tons), providing widespread consensus for the creation of a navigation channel . However, shipping traffic has since been far lower than expected--shipments of commodities including produce, manufactured items, lumber, and oil averaged only 683,000 tons (616,000 t) per year from 1994 to 2006 . </P>

Where does the missouri river start and stop