Going against the flow

So this guy told me that the Missouri River flows to the Gulf of Mexico, i.e., the Mississippi flows into the Missouri and not the other way around. "Why do you say that?" I replied. "I've looked at the maps," he said.

Has there been a conspiracy all these years to rob the Missouri of its glory?
Is the Mississippi "Father of Waters" title tainted?
Will I live long enough to uncover all the lies my teachers told me?
What happens when two worlds collide?
This happens.