Maps based on census data use counties as the dividing lines. This religious belief map is typical.
Counties are ENTIRELY DIFFERENT UNITS west and east of the Dry Line. East of the line, counties are about the same size, so they’re practical units for illustrating poverty or religion or voting patterns. You can see relative dominance or patterns of change easily. West of the Dry Line, most counties are HUGE. This leads to wild inconsistencies. Half of Arizona looks like one religion or one party, appearing as a significant part of the nation even though it contains a few thousand people. A similar sized HUGE county near Los Angeles contains 3 million people. In the east, an area this size would cover two or three states including a hundred counties.
There must be a more consistent way to show locations without unjustified fudging. Maybe mark each county as a dot on its county seat, then blur the zones between the dots?
Polistra's Mill 