BASED ON THE MAPS ANSWER THE FOLLOWING QUESTIONS. When La Salle claimed Louisiana for France, he was defining a region. He claimed all of the land drained by the Mississippi River and all of the river’s branches. This area is called the Mississippi River Basin—the region from which water flows into the main river. Many countries want to control the entire basin of their most important rivers, but few actually do. Why might it be important for a country to control the Mississippi River basin.