Good Point Ed II or The Protestant Ethic and the Spirit of American Capitalism
Brad DeLong links to Mark Thoma who Links to Ed Glaeser and Bryce Ward
"Blue State culture reflects primarily the legacy of different ethnicities working together at high densities: the most important historical explanatory variables are the share of the labor force in manufacturing in 1920 and the share of the population that was foreign born in 1920 strongly predict liberal beliefs and voting for John Kerry. ..."
The idea is that all those immigrants made xenophobia and religious intollerance very costly. People in Blue states learned to live and work with people of different nationality and religious denomination. I haven't read the paper and don't think it is really possible to statistically distinguish the variables stressed by Glaeser and Ward from religiousity and the legacy of slavery.
Still I have one other way of looking at the data -- Religiousity vs Religious uniformity. It is possible that people were just as devout in Blue states as in Red states, but they are devout in many different ways. I think it is possible that support for separation of church and state, religious toleration, and toleration generally in blue states is due to sectarian diversity. In 1900 Blue states had a large catholic minority and a not totally tiny Jewish minority.
Thus I guess one thing. There is probably a strong negative correlation between state economic growth up until 1973 and the fraction of Protestants in the state making Max Weber turn over in his grave. Don't worry Max, the causation is presumably growth causes Catholic (and numerically insignificant Jewish) immigration.
Another way of putting it is "The Blue states are the Jew states," but I'm not sure that is PC enough for the title (I confess I am not Jewish even though most people assume I am since I am very short and swarthy and have a germanic surname. Actually my ancestors include a long string of evangelical ministers).
This is interesting, since sectarian bigotry is one of the few faults that right wing Christian televangelists do not proudly proclaim. They insist that the have a common cause with conservative Catholics and orthodox Jews. I think they are telling the truth (for once). I think that, in the modern West, both the Catholic Protestant conflict which spilled oceans of blood in the 16th and 17th centuries and the war against the Jews which involved oceans of Xyclon B in the 20th century are well and truly over.
In fact, I agree with the many people whose names and URLs I forget who argue that religious intollerance has returned as a powerful political force in the USA exactly because the religiously intollerant have learned to tollerate each other the better to focus their fire on those who do not follow the faith of their fathers either because they are not religious enough or because they do not accept the shared traditional teachings of the various sects on sex.