This volume serves as the definitive reference companion to the multi-volume New History of Ireland, providing the essential data required to contextualize the political and social evolution of the nation. The editors, led by the late T. W. Moody, compiled this work to function as a rigorous scholarly apparatus for researchers and students of Irish history. By synthesizing complex genealogical records, historical maps, and administrative lists, the text provides a structural framework that supports the broader narrative of the series. It acts as a primary tool for verifying historical figures, territorial boundaries, and institutional successions across centuries of Irish development.

Historians and researchers regard this volume as a foundational reference tool for any serious study of Irish history. The text is noted for its high level of academic density and its meticulous attention to archival accuracy.