This map shows US Counties in 1970 (top) and 2011 (bottom), for all intents and purposes*, and the percentage of adults who had a high school diploma or less in those years. You can hover over a county to see the data in a popup box.
Use the filter at the top right to select counties by their 1970 rate to see if they've made progress. You'll probably find that almost every county has; those that used to be dark blue are now lighter blue, or even orange. Select the highly educated counties in 1970 (any small city with a Big 10 University would do) and you'll see they're still up there, as you would expect. So that's good.
But after doing that, use the second filter to select counties by per capita income in 2011. What do you see? Anything we can hypothesize about what this might tell us?
*The data are county level data from The Rural Atlas (education) and Census Bureau (income). Data listed as 2011 are actually from the American Community Survey, 2007--2011.