What is the large body of water into which the Mississippi River empties?
The Mississippi River empties into the Gulf of Mexico.
The Mississippi River flows from north to south, running through many Midwestern US states. It empties directly into the Gulf of Mexico. It NEVER empties into ANY ocean. The State of Florida separates the Gulf of Mexico from the Atlantic Ocean; The Mississippi River is far away from both Florida and the Atlantic! Water currents from the Atlantic flow into the Gulf south and southwest of Florida, especially during hurricane season.
There are two answers to this question based upon the way it is written. A. A large natural stream of water emptying into a large "body" is called a river; and B. A large natural stream of water emptying into a larger body can be called a tributary. Normally this is a smaller river than the "large body". Thus the Missouri River is a tributary of the Mississippi River.