When rivers are color coded according to name or some attribute, they river symbol and designation should be part of the legend. Some data sets do not lend themselves to nicely distributed classification maps. It is possible that the data have only a few high-value states, a few medium, and the rest are low, giving an apparently imbalanced map. Try various classification schemes and see if a better map can be made, but be careful not to force the data into misleading classes. Borders and Neatlines 1.
Borders are heavier than neatlines.
Neatlines should not be too thin and weak. Very thick borders with medium thick neatlines normally is too heavy. The neatline should be fairly close to the border. When placed too far inside the map area, it becomes a separate feature from the frame in which the map exists. Some sort of symmetry is required.