The O'Conors of Milltown, barony of Castlereagh, county Roscommon, share a common ancestry with the O'Conors of Dundermott and appear to have been resident at Milltown from the mid 18th century. Gormley states that the O'Conors acquired this estate on the death of Gerald Dillon of Dillon's Grove who had been granted it and whose daughter Mary had married Thomas O'Conor. The Milltown branch held lands in the parish of Kilcroan, barony of Ballymoe, county Galway, in the mid 1850s. Roderick O'Conor was one of the principal lessors in the parish of Kiltullagh, barony of Castlereagh at the time of Griffith's Valuation. In the 1870s Roderick Joseph O'Conor of Milltown, Tulsk, county Roscommon, owned 384 acres in county Galway and 1,496 acres in county Roscommon. In 1909 the O'Conors were negotiating with the Congested Districts' Board for the sale of almost 2,000 acres of their estate in counties Roscommon and Galway.
- Copy of confirmation of arms to Aylward Robert O’Conor of Somerton Lodge, Dun Laoghaire, great grandson of Roderick O’Conor of Milton, 4 July 1932. GO MS 111d: 85-86; National Library of Ireland
- S.R. & C. Walker, solicitors' collection (1962), contains abstract of title Roderick J. O'Connor to Milton etc, co Roscommona & Ardagh etc, co Galway, (documents cited from 1759) with 2 rentals 1868. M.6104; National Archives of Ireland
Contemporary printed sources
- HUSSEY DE BURGH, U. H. ''The Landowners of Ireland. An alphabetical list of the owners of estates of 500 acres or £500 valuation and upwards in Ireland''. Dublin: Hodges, Foster and Figgis, 1878. [available online at www.askaboutireland.ie] : 347
- PARLIAMENTARY PAPERS. ''Return of owners of land of one acre and upwards, in the several counties .... in Ireland''. HC 1876, LXXX: 298
- PARLIAMENTARY PAPERS. '' 18th Annual Report of the Congested Districts' Board for Ireland'', [Cd 4927] HC 1909, xvi. Appendix XXXII: 141
- ''GRIFFITH'S VALUATION OF IRELAND'[Primary Valuation of Tenements]', 1850-1858. : Castlerea Union, 25 (Milltown)
- LEET, Ambrose. ''A directory to the market towns, villages, gentlemen's seats, and other noted places in Ireland''. Dublin: Printed by B. Smith, 1814 : 287.
- LEWIS, Samuel. ''A Topographical Dictionary of Ireland''. London: S. Lewis & Co., 1837: Vol.I, 188.
- ORDNANCE SURVEY NAME BOOKS, County Roscommon: Vol. I, 89.
- WELD, Isaac. ''Statistical Survey of the county of Roscommon''. Dublin: Royal Dublin Society, 1832. : 486.
- TAYLOR, George & SKINNER, Andrew. ''Maps of the Roads of Ireland, surveyed in 1777 and corrected down to 1783''. Facsimile of 2nd edition. Shannon: Irish University Press, 1969: 72 (Milltown - no proprietor's name given)
Modern printed sources
- BURKE, Sir Bernard. ''A genealogical and heraldic history of the Landed Gentry of Ireland''. London: Harrison & Sons, 1904: 449-450
- MATTHEW, H.C.G. and HARRISON, Brian (eds). ''Oxford Dictionary of National Biography''. Oxford: University Press, 2004: Roderic J. O'Conor. XLI, 477-478
- GORMLEY, Mary (ed). ''Tulsk parish in historic Maígh Aí''. Tulsk, county Roscommon: [the author], 1989. : 82 & 147
- ''The Irish Genealogist'': DILLON, Gerald. Cnoc Diolun. A genealogical survey of the Dillon family in Ireland. II No.12 (July 1955), 361-367
- ''The Irish Genealogist'': CASTELEYN, Mary. The O'Briens of Fairfield, Co Galway: the O'Brien relations of Florimond, Comte de Basterot''. XI No. 3 (2004), 190-204