At the time of Griffith's Valuation William Calvert held lands in the parish of Clooncraff, barony and county of Roscommon, parts of the estates of Gilbert Conry and James Dillon. Lands amounting to 172 acres in the parish of Kilgefin, barony of Ballintober South, county Roscommon, the estate of William Calvert, were advertised for sale in June 1866 on his own behalf and as trustee for sale for George and Joseph Walpole. The sale included larger acreages in county Tipperary and King's County (county Offaly). In the 1870s William Calvert of Monkstown, county Dublin, owned 1,180 acres in county Roscommon.
National Archives of Ireland:
Landed Estates’ Court Rentals (O’Brien), Calvert & Walpole, 7 June 1866, Vol 81, MRGS 39/039, (microfilm copy in NUIG)