Thanks very much to DK of the Newberry Library, who was kind enough to drop me a note about the recently-completed Digital Atlas of Historical County Boundaries from the Newberry Library. This atlas is organized by state and documents every change in US counties from 1634 to 2000. This makes my little genealogist heart go patter patter patter. The maps are a little clunky, but the work that must have gone into this is unbelievable. I forgive slightly clunky maps. The project is available at http://publications.newberry.org/ahcbp/.

You start with a map of the US. Pick a state and you’re off and running. When you first pick a state you’ll get lots of options, including links to a full list of all counties ever to have existed in the state with historical details, commentary, and a bibliography with sources. There’s also an option to look at an interactive map of a state, and that’s where I spent my time.

The map lets you choose a date, then gives you a state map with two sets of boundaries: black lines for historical boundaries, and white lines for modern boundaries. A series of checkboxes lets you specify map layers — you can include the modern county names, look at modern county seats, proposed counties, and so on. Be sure to use the Refresh Maps button — this ain’t Ajax. Sometimes it’s a little hard to read the modern and the historical county names together on the same map, so I had to switch that layer on and off when looking at some states.

A nav on the left lets you move around the map a bit, as well as get individual county information, data on groups of counties, and details about county formation and existence.

If you are doing genealogy research and you go back far enough, you are at some point going to find yourself confused with county designations or location. Just looking around in this atlas for a few moments explained something I had always wondered about Virginia and why Brunswick County suddenly vanished from my genealogy notations around 1780, to be replaced with Greensville.

The maps are not as slick as the more modern maps, but really, who cares? This resource is free and the information is amazing. The only thing I would recommend (and I’m not sure this is possible) would be some way to link from a historic county outline to a modern Google Map, in order to get information on city and town locations. TERRIFIC STUFF.