Sebastian Sauer has a quick example of using ggcounty to plot data on a map of US counties:
This posts shows how easy it can be to build an visually pleasing plot. We will use hrbrmster’s
ggcounty, which is an R package at this Github repo. Graphics engine is as mostly in my plots, Hadley Wickhamsggplot. All build on R. Standing on shoulders…Disclaimer: This example heavily draws on hrbrmster example on this page. All credit is due to Rudy, and those on whose work he built up on.
In just a few lines of code, you can have a pretty nice map.