Very Interesting Migration Map

It is derived from IRS data about taxpayer moves from year to year.  You can click on a county and see how many people moved in (and from where), and how many moved out (and to where).  As might expect, some counties have huge numbers of people moving in and out, usually because they are high population counties.  What I found quite interesting is how some counties have population flows across the nation (such as the counties around D.C.), while many of the upper Mid-West counties have flow entirely between two or three counties that are contiguous (Shannon County, South Dakota).  One of the more interesting flows involved Whatcom County, Washington, with a surprising flow from Dade County, Florida--about as far as you can get from there in the lower 48!