Development Board for Rural Wales records, containing minutes and other papers of the Board and various committees, 1977-1994; general administrative files concerning the establishment of the Board, its functions and responsibilities, and correspondence with other organizations, 1966-1990; construction files containing correspondence, contracts and estate plans relating to housing and industrial developments executed by the Board, particularly in Newtown, 1968-1993; records such as correspondence, minutes, notes and other papers relating to research studies on economic and social life in Mid-Wales carried out by the Board, 1968-1995; files relating to the Board's marketing and promotional strategy, 1978-1991; and press releases, 1977-1990; Mid-Wales Development Corporation records, 1962-1979, including annual reports, 1969-1977, minutes and papers of the Board and various committees, 1968-1979, and seal registers relating to MWDC projects, 1968-1976, containing compulsory purchase orders, contracts, leases and other documents.

An additional three files relating to the Development Board for Rural Wales, being DB/CF/101/1; DB/CF/101/2; DB/CF/101/3 – (Extension to Goodall & Swanwick factories at Dolgellau; factories at Dolgellau; and extension to Marian Park Industrial Estate, Dolgellau). These remain uncatalogued, and are closed for ten years from the date of the latest document in each file.

Papers of W. A. Madocks, including his memoranda books, letters to John Williams (his agent at Portmadoc), 1806-1825, and some materials for his biography in the form of copies of letters from Ebenezer Thomas (`Eben Fardd'), John Thomas, Chwilog, Ellis Owen, Cefnymeusydd, and others; a 'statute book' of the 'Ancient and Renowned Borough of Tremadoc', 1805-1810, with an account of the Tremadoc Ball and Hunt; together with records from the Harbour Office, Porthmadog, including account books and registers of Portmadoc harbour, 1824-1917. Also included are records of the Festiniog and Blaenau Railway Co., 1866-1883; plans, sections and other records, 1860-1897, of the Aberystwyth and Welsh Coast Railway, the Bala and Festiniog Railway, the Beddgelert Railway, the Caernarvonshire Railway, the Caernarvonshire and Nantlle Railway, the Cambrian Railway, the Corris, Machynlleth, and River Dovey Tramroad, the Corwen and Bala Extension Railway, the Croesor Railway, the Croesor and Portmadoc Railway, the Festiniog Railway, the London and North Western Railway, the Merionethshire Railway, the Portmadoc, Beddgelert and Rhyd-ddu Railway, and the West Midland, Shrewsbury and Coast of Wales Railway; a register of shareholders and minute books of the Festiniog Refreshment House Company, 1878-1890; a minute book and share ledger of the Penrhyndeudraeth Lead Mining Company, 1875-1882; nominal and muster rolls of the Caernarvonshire Volunteers, 1860-1883, and other Caernarfonshire militia records; a minute book and papers relating to collections in Caernarfonshire towards Queen Victoria's Jubilee, 1886-1887; account books relating to slate quarries and to shipping, and miscellaneous Caernarfonshire material, 1723-[19th century].

Deeds, documents and plans, 1455-1895, relating to properties in Anglesey, Caernarfonshire, Denbighshire, Merionethshire and Montgomeryshire; including papers of the Poole family, owners of the Caenest and Pencraig estates in Merionethshire and Anglesey; surveys, [c. 1770] of the Caenest and Pencraig estates; and building leases for properties in the port of Amlwch, [late 18th century].

Records and papers collected by Emrys Roberts, 1945-1983, including correspondence and papers relating to the National Eisteddfod, 1959-1976; the Development Board for Rural Wales, 1973-1981; and Wales (West and North) Television Ltd, 1960-1967. There are also papers relating to other committees on which Emrys Roberts sat, 1967-1983, and other miscellaneous papers, 1945-1981.

Miscellaneous papers mainly of Anglesey and Merioneth interests. They include pedigrees, tax receipts, and a copy of 'Thos. Love Peacock's letter to Miss Jane Gryffydh of Caenycoid Festiniog'.

Family papers of the Williams family of Castell Deudraeth, 1859-1929, including a bound volume containing papers, including letters and press cuttings, relating to the general election of 1859 in Merionethshire in which David Williams stood as a Liberal against the sitting Conservative Member W. W. E. Wynne of Peniarth; scrapbooks, 1903-1929, containing press cuttings concerning the family, notably Sir Arthur Osmond Williams, and two typescript essays.

Papers relating to families and estates in north Wales, including the West family, the Chirk Castle estate, the Hengwrt, Rug and Nannau estate, the Wynnstay estate, the Penbedw estate, the estate of Richard Willding of Llanrhaeadr Hall, Denbighshire, and the Whitehall-Davies family of Broughton Hall, Flintshire, and Llannerch, Denbighshire. Records and correspondence, including relating to abstracts of title, chapels, churches, conveyances, inclosures, industrial activity, law suits, mining, parliamentary elections, probate, railways, schools and tithe commutation. Office records, including cash journals, bill books and letter books, [19th century]-[20th century].

Electoral lists of the commotes of: Ardudwy Uwch Artro, 1860-1861; Ardudwy Is Artro, 1861; Mawddwy, [1860s]; Tal-y-bont, 1861-1863; and Ystumanner, 1860; and jury lists for the parishes of Beddgelert; Dolgellau; Llanfihangel-y-Pennant; Llanfihangel-y-traethau; Llanfrothen; Llangelynnin; and Trawsfynydd, 1866.

Deeds and documents of the Bennett family of Glanyrafon, Montgomeryshire, and the Owen family of Dolgoed and Llawrpenegoes, 1546-1946, relating mainly to properties in the parishes of Llanidloes, Llanwrin, Penegoes, and Trefeglwys, Montgomeryshire, and Talyllyn, Merionethshire; and a map of properties in Trefeglwys, 1819.

Deeds, 1490-1977, including deeds and documents mainly relating to properties on Anglesey, Caernarfonshire, Merionethshire and Middlesex, 1675-1977; and deeds relating to properties in Finchley, Middlesex, 1490-1796.

(With 173B). Two volumes of rough transcripts, abstracts, extracts, etc. by J. H. Davies, with one transcript by E. A. Lewis, of original material (14c-19c), mainly relating to Caernarvonshire and partly to Anglesey and Merioneth, extracted mainly from public records. Other sources include manuscripts in the British Museum; Bangor episcopal lease books, surveys and rentals in the possession of the Welsh Church Commission (now in the National Library of Wales); and printed matter.

The series comprises small notebooks which Condry carried with him, recording descriptions of places visited, observations on wildlife, particularly birds and plants, geology, industry, historical landmarks, archaeology, personal reminders, ideas for writing and lecturing, photography, bibliographies, useful contacts and conservation issues, 1952-1994. The main geographical areas covered are Bardsey Island, Cader Idris, Cardiganshire and Merionethshire. An index to the series is provided., compiled by Ceridwen Lloyd-Morgan, 2013.

Papers relating to the administration of the Plas Power estate and household, including some properties belonging to the Chirk estate, some but not all of which became part of the Plas Power estate; also included are some records from other properties in England that were owned by the Myddelton family.

Personal papers of Sir John Williams comprising notes, essays, lectures and transcripts by him, [19th century]-[early 20th century]; certificates and testimonials, 1858-1915; cards and letters from the children of King George V and invitation cards to royal functions, 1889-1916; documents relating to his various honours, 1894-1911; photograph and stamp albums, 1849-[early 20th century]; other photographs, [1840s]-1905; press cuttings, [c. 1870]-1926; letters collected by Sir John, 1633-1912; letters to him, 1879-1922, the correspondents including members of the Royal Family; deeds and other documents relating to properties in Llangadog, to Plas Llanstephan and to Harley Street, London, 1790-1918; bibliographical material, [19th century]-[20th century]; medical notebooks and other papers, 1855-1900; diaries of Sir John and Lady Williams, 1872-1925; estate and financial records, 1890-[1926]; papers relating to public affairs, 1870-1911; miscellaneous items collected by Sir John, 1795-[c. 1919]; personal possessions, including University and commemorative medals, insignia, medical equipment, and ceremonial trumpets, 1861-1913; and deeds collected by Sir John Williams, 1546-1869, comprising deeds of the Vaughan family of Llanelli, Carmarthenshire, the Penry family of Swansea, Glamorgan, and the Dalton family of Pembrey, Carmarthenshire, 1545-1677, relating to properties in Llangennech and Pembrey, Carmarthenshire; deeds of John Jones, Ystrad, Carmarthenshire, relating to Llansadwrn, Carmarthenshire, 1632-1793, and the borough of Carmarthen, 1611-1869; Wynn of Gwydir deeds, 1352-1797, relating mostly to Caernarfonshire, Merionethshire and Denbighshire; miscellaneous Welsh deeds, relating mainly to properties in Carmarthenshire and Cardiganshire, 1451-[c. 1840]; and miscellaneous deeds relating to England (mainly Cornwall and Staffordshire), Ireland, and Scotland, 1586-1896.

Papers, 1679-1983, of and accumulated by H. Noel Jerman, comprising: research papers, 1914-1975; files relating to his work in the Secret Intelligence services, 1941-1945; correspondence, notes and other papers relating mainly to archaeology, and also to his professional activities, 1948-1983; 'Notes and Memoranda' relating to events organised by the Cambrian Archaeological Association, 1883-1894; original records collected by him, 1679-1926, including deeds and documents relating to properties in Kerry, Montgomeryshire, 1679-1885, and Kerry School, 1843-1873, and copies of local newspapers, 1834-1868; records relating to the Dolforgan estate, including deeds and documents relating to properties in Montgomeryshire, Carmarthenshire and Merionethshire, 1807-1910, financial records, 1889-1939, and letter books, 1892-1930.

An additional consignment of materials of, and accumulated by, the late H. Noel Jerman (1909-1994), including his research papers relating to properties in Kerry and surrounding areas, papers relating to the Dolforgan estate, together with maps, sale catalogues, plans and photographs, and a lithograph of Dolforgan Hall by T. Way. This group remains uncatalogued.

A volume, 1906, containing lists of communicants in the Diocese of Bangor, relating specifically to Montgomeryshire and Merionethshire.

Ledger and journal of Gaewern Slate works, Machynlleth, 1835-1856; accounts and notebooks of the Ratgoed and Cymerau Slate Quarries, Tal-y-llyn, and Llwyngwern Slate Quarry, Llanuwchllyn, 1853-1899; ledgers and notebook of the Cambrian Slate Works, Machynlleth, 1899-1909; minute books of the Abercorris Slate Quarry Company, Rhiwgwreiddyn, Corris, 1893-1909, and the Towyn Company, Tywyn, 1893-1903; and miscellaneous accounts and ledgers, 1827-1909.

Deeds, documents and probate records, 1617-1853, relating mainly to the parishes of Caerhun, Conwy, Dwygyfylchi, Gyffin, Llanbedrycennin and Llannor, Caernarfonshire, and to the Abbey estate, in Denbighshire, Merionethshire and Caernarfonshire, 1811-1819; notes on sermons, 1861-1889; and miscellaneous papers relating to Amlwch, Anglesey, 1801-1868.