From the announcement:
Today the Mapping Early American Elections team is making their final release of maps, data, and essays for this project. We have four main elements that we are adding to the site, in addition to the hundreds of state-level maps of Congressional elections during the first-party system that we have already released.
First, we are publishing six essays and a bibliography that give you an overview of the history of early American politics and a guide to how to use and interpret these maps for yourself. Here are the subjects of the essays.