As requested in comments here, I’ve produced a map of Tennessee county growth rates; here it is in Adobe PDF format. (Once I had the code written for Mississippi it was trivial to produce one for Tennessee.)
I’m still working on a southeastern U.S. map, but it’s made much more complicated because I can’t figure out a way to toss out the Virginia independent cities, which aren’t in the map data in the maps
package, from the census data in R. I may just edit the raw data file before reading it in.