First published in 1872, with a second edition in 1875, Nicholas's "Annals and Antiquities of the County Families of Wales" is still the standard work on Welsh family history and the chief source of genealogical data on the counties and families of the principality. Unlike other books on the subject, it combines histories of the ancient counties of Wales with family lineages, integrating the two to show the social and genealogical evolution of the country. Again unlike other works, it is based on the author's personal investigation of county records and family papers, producing in the end what can only be described as the most complete and faithful compendium of Welsh family history ever published.