Manuscripts comprising drafts of the hitherto-unpublished portions of Edward Owen's Catalogue of manuscripts relating to Wales in the British Museum, with draft indexes; reports prepared by Edward Owen on Liverpool Town Dues and related papers, 1931; essays written by him for the London Eisteddfod, 1887, and the National Eisteddfod at Caernarfon, 1894; notes, pedigrees, transcripts and letters relating to Welsh history, antiquities, county history, families and individuals such as John Edwards of Chirk, and historical figures including Owain Glyndwr [some items published 1893-1935]; transcripts and extracts relating to the history of Wales taken from public records by Edward Owen, E.A. Lewis and others, including several land surveys, at least one of which was used as evidence before the Royal Commission on Land in Wales, 1895; transcripts of papers by or relating to Alfred Neobard Palmer, Wrexham, 1885-1922; facsimiles and original documents including Privy Purse Accounts of Queen Anne, 1702-1710, and a holograph letter from Queen Anne to Sarah, duchess of Marlborough, 1710; letters mainly addressed to William Edwards of Chirk Hall, 1675-1677; autograph letters, mostly addressed to Edward Owen, 1886-1943; and deeds, 1463-1769, the majority of which relate to the estates of the families of Edwards of Plas Newydd and Puleston of Emrall in cos. Denbigh and Flint.

Correspondence and genealogical notes and papers relating to the Pierce family of Meiriadog, Denbighshire, later of Cwybyr, Flintshire, 1841-1936; leases and a few other documents, 1596-1764; autograph letters of David Jones, Llangan, 1800, and Rice Owen Jones, Blaenau, 1815; correspondence and financial accounts relating to barques and ships, 1873-1885; and letters, 1934-1936, relating to a stained glass memorial window for Llandrillo Parish Church, Denbighshire.