- The Costellos were settled at Castlemore, parish of Castlemore, barony of Costello, county Mayo, from at least the early 16th century. Castlemore continued to be their residence until the late 18th century but by the early 19th century the main family residence was at Edmondstown. Most of the Costello estate was in the parishes of Aghamore and Kilcolman, including one townland in the barony of Frenchpark. In 1862 Arthur Robert Costello, son of Charles, advertised for sale in the Landed Estates' Court about 1100 acres in the baronies of Gallen and Costello, county Mayo and about 1050 acres in the parish of St Johns, barony of Athlone, county Roscommon. Some of these lots were purchased in trust by Messers. McNevin and Burke. In the 1870s however he still owned 7513 acres in county Mayo and 1038 acres in county Roscommon. In July 1876 lands belonging to Charles Costello in counties Roscommon, Longford and Westmeath were offered for sale in the Landed Estates Court. Over 700 acres at Carrowmorragh, county Roscommon was purchased by P.F. Leonard. The Costello estate at Edmondstown was sold to the tenants in the 1880s and the house to the Bishop of Achonry. In 1878 Charles Costello of Kilfree, Gurteen, county Sligo owned 174 acres in county Mayo and 1330 acres in county Sligo. Most of this property was in the barony of Coolavin. After 1909 an offer was accepted by J.P. Costello on over 180 acres of his estate in county Sligo.
Dowell (Co Roscommon)
- In the 1850s Miss Eliza Dowell held a townland in the each of the parishes of Kiltoom and Taghboy and 2 townlands in the parish of St Johns, barony of Athlone, county Roscommon, apparently from Patrick John Blake. Her estate amounted to approximately 1,500 acres. At the time of the first Ordnance Survey the proprietor of the land in the parish of Taghboy was Mr S. Dowell.
Blake (Killiaghan & Gort)
- In 1863 Patrick John Blake advertised for sale the lands of Killiaghan and Gort, parish of St Johns and Cronin, parish of Taghboy, barony of Athlone, county Roscommon, which he held in fee and the Costello lands in the parish of St Johns which he held on a lease in perpetuity. All these lands were leased to the Dowells at the time of Griffith's Valuation.