Here’s a map, if I didn’t miss it earlier: Red states and blue states - Wikipedia
It’s interesting that the political map follows some geographical features that have not already been mentioned. In the southern US, blue counties follow the contours of the fertile soils of the old Cotton Belt and the upper part of the Mississippi Delta, where plantation agriculture, and now the black population, is concentrated. Conversely, the Appalachians, which had poor soils, are mostly red, having been settled mainly by poor whites.
Conservative correlates with rural and Liberal correlates with urban, which correlates with transportation hubs, which correlates with rivers and sea ports.
Another factor which DrCube didn’t mention is the idea that people who live in cities accustomed to the idea that the nearest police officer is probably less than a mile away but people in the country may find that the nearest police officer is several dozen miles away. Consequently, rural people are more likely to embrace the idea of taking the law into their own hands rather than enlisting the help of the police to enforce the laws.
I think there’s something wrong with that map I linked to. It has El Paso county (TX) marked red. That’s a very blue county. And it’s blue on this map (click “county leaders”). Am I missing something here?
Here’s another map according to counties for the 2012 Presidential election:
As you can see, it’s basically rural vs. urban, not inland vs. coastal. Yes, there’s a small tendency toward inland being more Republican and coastal being more Democratic, but that’s because the coasts have more cities. It would take a book to explain the history of why the present distribution of party voters is the way it is.
An interesting exception: In the Mountain and northern Great Plains states, the blue counties are mainly those containing Indian reservations, which are both rural and mostly very poor.
Another exception is some rural counties with large Hispanic populations.
This is not how it works in WA, http://www.thestranger.com/seattle/welfare-state/Content?oid=6686284
I suspect this is true for most of the country as well. The irony runs deep.
A better correlation seems to be population density – generally, the denser the population, the more blue the votes.
If you look even closer, at precinct-level maps, you can see this in urban areas – the core city will be heavily blue, inner suburbs are lighter blue, middle ring suburbs are purple, and outer suburbs turn red. And in rural areas, the towns (even small ones of a thousand people or so) are less red than the outer areas.
There are exceptions, like already mentioned areas of high-minority population (hispanic, black or native american) are blue even with low population density, and there are some suburbs of well-off, highly-educated liberals that vote blue. But in general. population density matches well to votes.
Here’s an article with several maps showing that rural areas (and red states) tend to receive more money from the federal government than urban areas (and blue states):