It occurs to me, regarding incarceration rates, that it would make sense to simply show per capita incarceration rates by state. So here you go - a map that is adapted, again, from Pew's One in 100: Behind Bars in America 2008 (pdf):
More so than in the map of prison funding, some clear geographical tendencies emerge here. One way to characterize the deepest blue states here would be as all the Gulf Coast states plus South Carolina, Oklahoma, Delaware and Arizona. Another way would be: the Deep South plus a few outlying states. Yet another would be: the states Goldwater won in the 1964 US presidential election, plus Texas, Oklahoma, Delaware and Florida. And another still would be: 10 of the 21 states (+ DC) with the lowest proportion of non-Hispanic whites.
I think all of these characterizations, actually, tell us something about why these states, in particular, have the highest incarceration rates: I mean, is anyone surprised that the Deep South has most of the highest incarceration rates in the country? But I think the last characterization is especially interesting. Look at this map based on data from censusscope.org:
Someone who actually knows a thing or two about statistics would be able to run some sort of regression analysis to check this hypothesis, but it looks to me like there's a pretty strong correlation between a state's incarceration rate and its non-white population, but that that correlation is somewhat mitigated by certain regional variables (if the state is in the Interior West, it will have a relatively high number of prisoners; if it's in the Northeast or Far West, a relatively low number). And actually, it might be more correct to say that the correlation holds for states with the smallest white majorities, since for three of the four states which actually have majority-minority populations (Hawaii, New Mexico, and California, but not Texas), the incarceration rates are not notably high.
And really, all of this is totally unsurprising, if you accept this premise: that most of what happens in American politics is inflected by race, and in particular, by the white majority's fears about non-whites. Given this premise, you would expect crime and punishment policies to tend towards the more punitive in places where a large minority population would seem to pose a threat to the white majority, since in those places the (white) majority will be more likely to support policies driven by emotional gratification (i.e., 'lock up the bastards!'). In such places, since non-whites tend to be poorer and have less social capital, the 'bastards' will tend to be equated with non-whites. (And indeed, the incarceration rate for non-whites is much, much higher than it is for whites (one of the strongest bits of evidence that we are still a long ways from a "post-racial" era).) But in places like northern New England, the Upper Midwest, and the northern Plains, non-whites constitute a minuscule portion of the population, so there's less racial anxiety among the white majority. And, since almost everyone in places like North Dakota and Vermont is white, it ends up being mostly white people that are sent to prison; it makes it a little harder to work up the old "lock up the bastards!" dander when the bastards in question (or in the mind's eye, at least) don't have a different (which is to say, dismissable and otherizable) racial identity from one's own.
This could also explain why three of the four states with the highest non-white populations - the aforementioned Hawaii, California, and New Mexico - aren't in the top quintile of highest incarceration rate states. In those states, whites are in the minority, so you'd expect them to be much less able to translate their collective interests into actual policy.
I don't mean to suggest that high incarceration rates are just a function of white racial anxiety. Like I said, there are regional patterns too - I don't think the high rates in the Interior West have especially much to do with race. And I guess it's possible that crime rates might be somehow related to the number of prisoners in a given state. But really: it's the United States we're talking about here. That pretty much means that race is a factor.