Take a look at the map of the locations of the Federal Reserve districts and their headquarters in Figure 15-6 on page 329. Today, the U.S. population is centered just west of the Mississippi River-that is, about half of the population is either to the west or the east of a line running roughly just west of this river. Can you reconcile the current locations of Fed districts and banks with this fact? Why do you suppose the Fed has its current geographic structure?