I'm going to scrap this map for a number of reasons.
The first reason is the map I'm using, which was assembled from shapefiles by
@Chicxulub and contained ugly borders and missing towns. I planned on fixing the errors as I went along, but they are so numerous and time-consuming to fix that I don't see the point now.
The second reason is the uniformity of the map once I got west of the Philadelphia suburbs. 90% of the towns left in PA were German, and almost everything west of that was German or Scandinavian, with pockets of other groups around big cities. If the map isn't going to say much more than a county map, why bother?
The third reason is the uselessness of the ACS data. The ethnic origin surveys are separated by race and use different methodologies, which results in biases towards Hispanics, African-Americans, and Native Americans, and against Whites and Asians. On top of that, in many small towns, the population of every group falls within its own margin of error.
The fourth reason is the diminishing number of Americans who know their own ancestry.'
However, I always have the 2000 ancestry question from the census form to fall back on, which suffers from being outdated but is both far more accurate and precise. I will use this data and follow
@FrankCesco's request for a map of the northeast using
@VT45's map, then produce a nationwide county map with my methodology and call it quits with this.
