The Erne papers comprise around11,750 documents and volumes, 1611 to 1981, some of them relating to the family and personal affairs of the Creighton family of Crom Castle, Newtownbutler, Co. Fermanagh, Earls Erne, but most of them relating to the administration of their various estates: at Crom, Callowhill, Derrylin, Killynick, Lisnaskea, Knockballymore and Enniskillen, Co. Fermanagh; at Lifford, Co. Donegal; and in Dublin City, Co. Sligo and Co. Mayo.
Most of the material relates to the period 1830 to 1950, with comparatively few documents for the 17th and 18th centuries. This uneven survival of material is probably due to the destruction of the original Crom Castle by an accidental fire in 1764, and to the subsequent absences from Crom of the family until the 1830s, although they did at the very least maintain a summer residence on Inisherk from around 1780 onwards. The main exception, in terms of early archival survivals, are the papers relating to the Balfour estate at Lisnaskea and elsewhere in Co. Fermanagh. This was not purchased by Lord Erne until 1821, so the documents relating to it were not destroyed in 1764, and in fact provide important information about early 17th century settlement. The Erne papers comprise such material as title deeds, settlements, wills, leases, rentals, accounts, maps, surveys, architectural drawings and Land Commission sale papers relating to the various properties, together with correspondence about estate, political and family affairs, 1727 to 1728 and around 1775 to 1945. Some family and estate correspondence has found its way into the National Library in Dublin (for example MS 15360).
The Creightons were created Earls Erne in 1789, but, from the succession of the 3rd Earl in 1842, seem to have styled themselves Earls of Erne. A further complication is that in 1872 they changed the spelling of their family name from Creighton to Crichton. The different renderings at different times have been observed in the text which follows.