Strange Maps has a good entry comparing a map of “blue” counties in the South from the recent election to a map of cotton production in the 1860s, and the overlap is striking.
In the South, most counties cast a majority of votes for John McCain, but a non-trivial number went for Obama. The Obama counties, as it turns out, have a significant correlation with the highest cotton producing regions in the 1860s.
The link between these two maps is not causal, but correlational, and the correlation is African-Americans. Once they were the slaves on whom the cotton economy had to rely for harvesting. Despite an outward migration towards the Northern cities, their settlement pattern now still closely corresponds to that of those days.
. . .
And while their votes did not swing their states towards â€˜theirâ€™ (2) candidate, the measure in which black residents of Louisiana, Mississippi, Alabama and South Carolina voted for Obama is remarkable in that this particular voting pattern still corresponds with settlement patterns of almost a century and a half ago.