Thom's Directories are an invaluable resource for researching family history. First published in 1844 by Alexander Thom, it is still being published today. The directory expanded quite rapidly, the first publication having about 1,000 pages, by this edition there was almost 2,000 pages. Much of the initial part of the directory is taken up with information relating to the United Kingdom and its functionaries. The full title of Thom's directory best describes this section: Thom's Official Directory of the United Kingdom of Great Britain and Ireland for the year 1880. Comprising British Foreign and Colonial Directories, Parliamentary Directory, Peerage, Baronetage and Knightage Directory, Naval and Military Directory, Statistics of Great Britain and Ireland. Government Offices' Directory, University, Scientific and Medical Directory, Law Directory, Ecclesiastical Directory, Banking Directory, Postal Directory, County and Borough Directory, Lieutenancy and Magistracy of Ireland. Post Office Dublin City and County Directory. It is a large list of the civil servants, politicians and ruling classes from the Queen down.
The bulk of the directory then focuses on Ireland. Beginning with statistics compiled from the previous census, there is also listings of landowners of 1,000 acres upwards, on a county by county level, followed by several hundred pages detailing various state officials, as well as other civil, military and religious officials in the country. Also included is a listing of clubs, societies and institutions.
The county by county sections provide statistical information compiled from the census, as well as the leading civil servants in each county, including local magistrates, Boards of Guardians of the Poor Law Unions, and information on the Petty Sessions and county fairs. The final portion of Thom's is made of information on Dublin City and County. Much of the information for the city is similar to that provided for the counties but it also includes a street directory listing inhabitants of each of the dwellings. This is followed by the county directory which extends from Balbriggan to Dún Laoghaire. It also includes many of the areas now considered part of Dublin city, such as Rathmines and Swords. Many of these areas include a street directory. This is followed up by a listing of the nobility, gentry, merchants and traders of the city and suburban areas. The directory is concluded with the Annals of Dublin, with details of important events in the city from 140 AD to the time of publication.