Last week, I spotted a blog post showing a pair of maps: one represented cotton production in the deep south in 1860 and another had Election 2008 results. Today, Strange Maps offers a composite of the two, pairing color-coded vote results by county with dots representing cotton yield (one dot equals 2,000 bales). The conclusion is unsurprising:

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 ‘their’ 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.

More maps: The Special Topics Cafe notes a nearly opposite trend in The Upland South, which was settled by Scots-Irish farmers and had fewer plantations.