In all genealogical work the first and most important step is to establish the geographical origin of the ancestor. In Irish research the genealogist may know the name of the county where the ancestor lived but be puzzled about a place name given as the place of birth or residence. In all probability the place-name is that of a townland, the smallest territorial subdivision in Ireland. Since research in Ireland will usually start at the parish level, there must be a reference tool that will key the townland to the parish in which it is located.

This work was prepared under the auspices of the British government for almost that purpose. The over 900 densely printed pages show the county, barony, parish, and poor law union in which the 70,000 townlands were situated in 1851, as well as the location of the townlands on the Great Ordnance Survey maps, with appendices containing separate indexes to parishes and baronies.