Papers, 1634-1928, mostly deriving from and relating to the legal practice of Henry Rumsey Williams, comprising draft conveyances, abstracts of title, letters, accounts and miscellaneous papers of clients, including the estate of Wynn of Glynllifon, 1719-1840, the Griffiths family of Caernarfon and Amwlch, 1726-[1830s], Jared Jackson, 1760-1836, Plasgwyn estate, 1761-1846, Cefn Cwmwd estate, 1763-1828, Coed Helen estate, 1770-1838, Trergo estate, 1771-1832, Parry family, 1773-1788, Peniarth estate, 1773-1830, Orielton estate, 1774-1814, Bodior estate, 1778-1837, Faenol estate, 1778-1840, Arnold Robinson Burrowes, 1785-1837, Grindley family, [c. 1786]-1842, Morgan family, 1787-1839, Treiorwerth estate, 1787-1844, Evan Pritchard, 1788-1813, John Price, 1790-1844 Caerhun estate, 1791-1834, W. A. Madocks, 1799-1824, Nancall estate, 1802-1837, Morris Griffith, 1804-1832, Edward Griffith Roberts, 1805-1827, William Humphrey, 1805-1833, Plas Llanfair estate, 1805-1837, Baily Williams family, 1806-1838, Richard Garnons, 1809-1837, Cefn Hengwrt estate, 1810-1815, George Bettiss, 1810-1831, William Edwards, 1811-1836, Penrhyn estate, 1811-1837, Wyatt family, 1813-1835, Gelli Goch estate, 1815-1831, Anna Maria Wynne, 1816-1833, Robert Thomas, 1818-1839, Roberts family, 1818-1840, Bodegroes estate, 1819-1836, Hughes, Brydges and Granville, bankers, 1819-1840, Vickers family, 1820-1833, Boston estate, 1820-1839, Owen Griffith, 1822-1846, George Holmes Jackson, 1823-1841, the Rev. Hugh Hughes Wynne, 1831-1848, John Rowlands, 1832-1841, and Edward Hosier Williams, 1833, in Caernarfonshire, Anglesey, Denbighshire, and Merionethshire; legal correspondence, 1790-1848, probate records, 1727-1871, and papers relating to civil cases, 1757-1850, religion, 1788-1842, mining, 1779-1842, quarrying, 1798-1840, shipping, 1778- [c. 1841], roads and railways, 1834-1839; legal practice records, 1804-1841, and executorship papers, 1841-1855, belonging to Henry Rumsey Williams, and records of his family in Brecknockshire, Monmouthshire and Caernarfonshire, 1881-1928. Records relating to William's political activities have not survived.

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].