Have you ever wondered what your county or Congressional district boundaries looked like in 1845? Before 1845? Then this is the blog post for you.
At UCLA, Jeffrey Lewis, Brandon DeVine and Lincoln Pritcher have developed and made freely available Congressional district boundaries for the entire lower 48 states – all the way back to 1789. Their project draws on research previously done by Kenneth Martis, who also provided advice and source materials for the authors. The boundaries are available as an ESRI shapefile and GeoJSON at a slightly lower resolution. Please visit their website for more information and documentation, as well as to download the shapefiles. The three maps below use their data to show the district boundaries at different points in time.
The project used data from the National Historic GIS, as well as the Newberry Library in Chicago. The Newberry Library provides GIS and KML files for historical county boundaries at the state and national levels. Take, for example, this page for Connecticut which explains the data and directs you to an interactive viewer that allows you to compare modern and historical county boundaries from various dates (see below).