Mapping the Republic of Letters is made up of a number of rich case studies. The case studies are strategic in geographic range and in time period, and in their breadth and scope. As we develop new case studies at Stanford and establish partnerships with groups developing digital correspondence projects, the number of case studies continues to grow. The wide range of case studies gives us multiple points of intersection with the Republic of Letters. Most every case study is based on a different information source and so each one one presents different problems of data handling as well as unique information visualization challenges.