This is a difficult question to answer, mainly because water flowing makes it hard to determine a “beginning” and “end” to rivers. The most used definition of the beginning of a river is the head of its first tributary, while it “ends” when it dumps into the ocean. Using this definition, most agree that the Mississippi river is about 2,300 miles long from the head of the Missouri river to where the Mississippi river dumps into the ocean.
However, this is the shortest the Mississippi can be. If you add other tributaries that flow into the Mississippi and into the Missouri rivers, you’ll have a lot more land. The problem there is that creates a branched off system, and most lengths have to be from point A to point B.
Estimates or measurements differ slightly from different , but it is at least 2,300 miles long along its longest tributary, the Missouri.
It must be measured from its source in Lake Itaska, Minnesota to its mouth in the Gulf of Mexico. The difficulty is finding a finite point in a body of water as 'beginning' or 'end'.
