How We Made This

This map takes advantage of Drupal's (our site's content management system) robust set of modules, which we can use to add all kinds of functions. We encoded placenames from the Southey Letters in an .xml file and then trained an OpenLayers module on the data to produce this map. You could get similar results using a dedicated mapping platform like ESRI or Carto, or an open-source data visualization program like D3.