<P> Deliberate water diversion at the Old River Control Structure in Louisiana allows the Atchafalaya River in Louisiana to be a major distributary of the Mississippi River, with 30% of the Mississippi flowing to the Gulf of Mexico by this route, rather than continuing down the Mississippi's current channel past Baton Rouge and New Orleans on a longer route to the Gulf . Although the Red River is commonly thought to be a tributary, it is actually not, because its water flows separately into the Gulf of Mexico through the Atchafalaya River . </P> <P> The Mississippi River has the world's fourth - largest drainage basin ("watershed" or "catchment"). The basin covers more than 1,245,000 square miles (3,220,000 km), including all or parts of 31 U.S. states and two Canadian provinces . The drainage basin empties into the Gulf of Mexico, part of the Atlantic Ocean . The total catchment of the Mississippi River covers nearly 40% of the landmass of the continental United States . The highest point within the watershed is also the highest point of the Rocky Mountains, Mount Elbert at 14,440 feet (4,400 m). </P> <P> In the United States, the Mississippi River drains the majority of the area between the crest of the Rocky Mountains and the crest of the Appalachian Mountains, except for various regions drained to Hudson Bay by the Red River of the North; to the Atlantic Ocean by the Great Lakes and the Saint Lawrence River; and to the Gulf of Mexico by the Rio Grande, the Alabama and Tombigbee rivers, the Chattahoochee and Appalachicola rivers, and various smaller coastal waterways along the Gulf . </P> <P> The Mississippi River empties into the Gulf of Mexico about 100 miles (160 km) downstream from New Orleans . Measurements of the length of the Mississippi from Lake Itasca to the Gulf of Mexico vary somewhat, but the United States Geological Survey's number is 2,320 miles (3,730 km). The retention time from Lake Itasca to the Gulf is typically about 90 days . </P>

What are the approximate eastern and western boundaries of the mississippi watershed