As we progress through the presidential election year, I'll be posting maps and spreadsheets showing how American political geography has changed over the past 60 years, and how those trends went into the making of the 10 Political Regions map. First, here are four very basic maps comparing 1948 with 2004 in terms of the percentage received by Democratic candidates in each county, and also in terms of the raw-vote margin between the two major parties. (Note that the Democratic vote in four states in 1948 -- Alabama, Louisiana, Mississippi, and South Carolina -- was mostly siphoned off by Dixiecrat candidate Strom Thurmond.) I'll be filling adding maps that show what went on between these two elections, as well as close-ups of geographical regions.
UPDATE: See 1960 maps here.