text: how much of the united states is drained by the mississippi river system ?   from wikipedia:  the mississippi river has the third largest drainage basin ("catchment") in the world, exceeded in size only by the watersheds of the amazon river and congo river. it drains 41 percent of the 48 contiguous states of the united states. the basin covers more than 1,245,000 square miles (3,225,000 km²), including all or parts of 31 states and two canadian provinces.