The Mississippi River is the second-longest river in the United States,with a length of 2,320 miles (3,730 km) from its source in Lake Itasca in Minnesota to its mouth in the Gulf of Mexico.
The Mississippi River is part of the Missouri-Mississippi river system,which is the largest river system in North America and among the largest in the world:by length (3,900 miles (6,300 km)),it is the fourth longest,and by its average discharge of 572,000 cu ft/s (16,200 m³/s),it is the tenth largest.
The Missouri River flows from the confluence of the Jefferson,Madison,and Gallatin and is the longest river in United States.Taken together,the Jefferson,the Missouri,and the Mississippi form the longest river system in North America.If measured from the source of the Jefferson at Brower's Spring,to the Gulf of Mexico,the length of the Mississippi-Missouri-Jefferson combination is approximately 3,900 miles (6,300 km),making the combination the 4th longest river in the world.The uppermost 207 miles (333 km) of this combined river are called the Jefferson,the lowest 1,352 miles (2,176 km) are part of the Mississippi,and the intervening 2,341 miles (3,767 km) are called the Missouri.
The Arkansas River is the second longest tributary of the Mississippi River.Measured by water volume,the largest of all Mississippi tributaries is the Ohio River.
The widest point of the Mississippi River is Lake Winnibigoshish,near Grand Rapids,Minnesota at over 7 miles (11 km) across.Also of note is Lake Onalaska,near La Crosse,Wisconsin,where the river is over 4 miles (6.4 km) wide (created by Lock and Dam No.7) and Lake Pepin at more than 2 miles (3.2 km) wide.[5] However,the first two areas are lakes or reservoirs rather than free flowing water.In other areas where the Mississippi is a flowing river (other than Lake Pepin),it exceeds 1 mile (1.6 km) in width in several places in its lower course.
Beginning with its source at Lake Itasca to Saint Louis Missouri,the Mississippi's flow is moderated by 43 dams.Fourteen of these dams are located above Minneapolis Minnesota in the Headwaters region and serve multiple purposes including power generation and recreation.The remaining 29 dams beginning in downtown Minneapolis all contain locks and were constructed to permit commercial navigation of the upper river.Taken as a whole these 43 dams significantly shape the geography and influence the ecology of the upper river.Beginning just below Saint Paul Minnesota and continuing throughout the upper and lower river,the Mississippi is further controlled by thousands of wing dikes that moderate the river's flow in order to maintain an open navigation channel and prevent the river from eroding its banks.
The Mississippi River runs through 10 states and was used to define portions of these states' borders.The middle of the riverbed at the time the borders were established was the line to define the borders between states.[6][7] The river has since shifted,but the state borders of Wisconsin,Iowa,Illinois,Missouri,Kentucky,Arkansas,Tennessee,and Mississippi have not changed; they still follow the former bed of the Mississippi River as of their establishment.
The river is divided into the upper Mississippi,from its source south to the Ohio River,and the lower Mississippi,from the Ohio to its mouth near New Orleans,Louisiana.