Take what you will from it, but:
“One should not put much weight on this purely “cross-sectional” evidence over one point in time and many factors determine murder rates, but it is still interesting to note that so much of the country has both very high gun ownership rates and zero murders.”
Correlation doesn’t prove causation. But it dosn’t mean that the correlated is wrong. Too many people use correlation as proof that it is irrelevant.
Russell Ward
The comments on the articles are interesting too.
It doesn’t take into account population density though. I wonder what that will show when factored in.
Just looking at the map without any context, I’d say it’s a map of population density.
It’s not really shocking to know there are more murders where there are more people. Why, I’d wager if there were a county with zero residents, it would have a low murder rate.
Some very thoughtful discussion in the commentary following the article as well.
Here’s what google says on population density.
Go Texas! 
US Population density by county, 2010:
Here are the 2 maps overlayed with the murder map changed to Blue.
Population may be part, but there are a lot of population centers that are not on the murder map.
How about throwing this into the mix.
Without the article.
The variation of that map is too fine of detail and have too many colors to easily discern when over layered on the other maps. Just too much shit. 