It was from a while back, maybe 2-8 years back, somebody designed basically a dot density map of light points, but removed the shape and lines of the United States map underneath it. The effect is cool, either liberal or democratic voters or else people who were pro-diversity were the only ones shown - so just one color of dot. It highlighted the coasts and the Mississippi River as zones that were more accepting of diversity, ostensibly because of all the trade routes meeting different types of people.