At the beginning of the 18th century William Conolly of Castletown, county Kildare, purchased over 2,000 acres in county Roscommon from the trustees for the sale of forfeited estates. In June 1867 the rental of the estate of Thomas Conolly, Member of Parliament, in the parish of Elphin, barony and county of Roscommon, was advertised for sale. The Irish Times mentions Messers Lyle and Ryan as among the purchasers. At the time of Griffith's Valuation the estate was mainly in the possession of Pierce Simpson. It was comprised of just over 1,000 acres. Some land in King's County (county Offaly) was included in the sale.
Irish Architectural Archive:
Castletown papers: 97/84 Box 78, 1694-1840: leases, letters and legal documents relating to county Roscommon lands.