The Mississippi River is the longest river in North America and it runs from Minnesota to the Gulf of Mexico, about 3,200 miles. The Mississippi River has been an important factor in the growth of wetlands in Southern Louisiana, because it carries thousands of tons of sediment (small rocks, sand and soil) from its watershed areas and causes the sediment to build up and form land in the area where the Mississippi River meets the Gulf of Mexico. Eventually plants and animals will start living on the land built by the sediment. The Mississippi River also carried important nutrients to the wetlands, and kept salt water from entering the wetlands from the Gulf of Mexico.
People have built levees and other structures to control the flow of the river. This effort to prevent flooding is important for people living in these areas, but it has also changed the natural behavior of the river. Some scientists think that this change is at least partially responsible for the loss of wetlands in Southern Louisiana.