The Mississippi River is the largest river system in North America. About 2,320 miles (3,730 km) long, the river originates at Lake Itasca, Minnesota, and flows slowly southwards in sweeping meanders, terminating 95 miles (153 km) by river below New Orleans, where it begins to flow to the Gulf of Mexico.
Along with its major tributary, the Missouri River, the river drains all or parts of 31 U.S. states stretching from the Rocky Mountains in the west to the Appalachian Mountains in the east to the Canada–US border on the north, including most of the Great Plains, and is the fourth longest river in the world and the tenth most powerful river in the world.
The current form of the Mississippi River basin was largely shaped by the Laurentide Ice Sheet of the most recent Ice Age. The southernmost extent of this enormous glaciation extended well into the present-day United States and Mississippi basin.
When the ice sheet began to recede, hundreds of feet of rich sediment were deposited, creating the flat and fertile landscape of the Mississippi Valley.
During the melt, giant glacial rivers found drainage paths into the Mississippi watershed, creating such features as the Minnesota River, James River, and Milk River valleys.
When the ice sheet completely retreated, many of these "temporary" rivers found paths to Hudson Bay or the Arctic Ocean, leaving the Mississippi Basin with many features "oversized" for the existing rivers to have carved in the same time period.
The Mississippi River Delta has shifted and changed constantly since the formation of the river, but the construction of dams on the river has greatly reduced the flow of sediment to the delta.
In recent years, the Mississippi's mouth has shown a steady shift towards the Atchafalaya River channel, but because of floodworks at the river's mouth, this change of course—which would be catastrophic for seaports at the river mouth—has been held at bay.
