Here's an interesting article in the NYT about a map showing slave populations in the South, compiled from the 1860 Census data - the high water mark for American slavery. And the last time a Census could even compile information on that particular demographic. Historian Susan Schulten notes,
The map uses what was then a new technique in statistical cartography: Each county not only displays its slave population numerically, but is shaded (the darker the shading, the higher the number of slaves) to visualize the concentration of slavery across the region. The counties along the Mississippi River and in coastal South Carolina are almost black, while Kentucky and the Appalachians are nearly white.
Translating numerical data into visual representations is one of the most powerful communication techniques available. The patterns just pop out at you. No wonder people were so taken with this map.
The presence of slavery, and (after 1865) large populations of African-Americans, wasn't the only thing peculiar about the South, though. There was a remarkable absence of foreign-born whites as well. Recently I was poring through the Statistical Atlas from the 12th Census of the United States -- that's from 1900, just to save you the arithmetic -- and came across this fascinating chart.
Click on the "Go to source" button to see it. The chart shows a breakdown of each state's population by race and origin. Four races are listed: Indians, Chinese & Japanese, Negro, and White (corresponding to the "Red and yellow, black and white" that I learned singing "Jesus Loves the Little Children" 'way back in Sunday School*). For whites, there are three further subdivisions: native white of native parents (baby blue), native white of foreign parents (pink), and foreign-born white (green). These were the categories that mattered in 1900.
Notice the states with the longest black lines - those are the Old South, the slave-holding South before the end of the Civil War, and the states that still held the majority of the nation's black population before the Great Migration. And in 1900, a period of intense immigration, most of those states had little to negligible pink and green in their bars. In other words, almost everyone who wasn't black was a white of at least the second generation. In a nation of immigrants, the South drew almost no immigrants.
According to the next couple of Censuses, little changed during the next 20 years. Bear in mind that this is one of the most immigration-heavy periods in US history. Yet the South missed it. They first developed enough of a separate identity to secede from the rest of the country, then learned to resent outsiders all the more intensely -- as you would, too, if you'd suffered invasion, defeat, and military occupation for a dozen years. And then they had the privilege, if privilege it is, of remaining insular while the rest of the country went through the wrenching experience of assimilating people who were as foreign as could be imagined (not only Chinese and Japanese, but Irish, Italians, Greeks, and so forth).
In respect to immigration and Americanism, it was even uglier 100 years ago than it is today. The "hyphenated American" (e.g., German-American) was no American at all, said Theodore Roosevelt, while Woodrow Wilson compared the hyphen to "a dagger that [the immigrant] is ready to plunge into the vitals of this Republic." The 1924 National Origins Act represented an unabashed attempt to keep the US not just white, but lily-white, by limiting the number of immigrants from unpopular nations.
The South didn't need the help, though. Aside from a few Yankee carpetbaggers, unwanted immigration wasn't part of their experience. Other people's families had been there just as long as yours and their brand of religion was probably the same as yours. No one had to accommodate diversity, when there were only two ethnic groups and their status was legally defined.
If it seems at times that Southern culture is especially prone to creating parochial mindsets, and people who steadfastly refuse to accept that not everyone thinks the same as they do -- and that is how Southern culture often comes across to me, at least as expressed in politics and the culture wars -- then maybe this is part of the reason why: no other region in the country was allowed to remain so culturally insular for so long a time.
* Which dates from about the same era, interestingly enough. This piano rendition renders the tune in fine 19th Century style.