I keep coming back to this region of the country: a strip running from West Virginia down the back (west side) of the Appalachians, through Kentucky and Tennessee, on through Arkansas to Oklahoma. I'm going to call it the Bad Stripe. Why? It's cloudier there, and people are less happy; and they also are about the only part of the country that voted Republican at higher rates in the 2008 race than they did in 2004. This is not an endorsement of one party or indictment of the other; but I would say, and I think self-described cultural conservatives would agree with me, that cultural conservatives are likely to be "angrier" than non-cultural-conservatives. Therefore, there are people are probably angrier in the more-Republican-2008-stripe than outside it.
The overlap is less exact here, but again the same Bad Stripe jumps out when looking at life expectancy. At first I thought that this map was just showing the Black Belt, but this graph is white male life expectancy:
It appears to be partly poverty, which shows patchy low-per-capita-income areas throughout that stripe.
But still: a) there are other poor parts of the country that are happier (southwest Texas) and b) many rural poor Western areas are both happier and healthier. The only thing that comes to mind is (say it with me) diet and exercise, the latter of which is much easier with the sun shining.