An estate of over 3,000 acres in the baronies of Clonmacnowen and Kilconnell, county Galway, was granted to John Donnellan by patent dated 6 Feb 1677/8. Burke states that the Donnellan families of Ballydonnellan, Nutgrove and Hillswood derive from him while the Donnellans of Ballyeighter descend from his younger brother, Richard.

Anthony Donnellan, Ballyeighter and Stephen Donnelan, Killagh, are recorded as resident proprietors in 1824. The Ballydonnellan estate, the property of Charlotte Donelan, was offered for sale in the Encumbered Estates court in July 1850. In the 1870s the Donnellan estate at Killagh amounted to over 1100 acres. For more information on the Donnellan estate see www.ballyd.com.

Property:
Ballydonnellan:
Ballydonnellan Castle, Ballydonnellan East townland, Killalaghtan Civil Parish, Ballinasloe Poor Law Union, Barony Kilconnell:
At the time of Griffith's Valuation, Ballydonnellan Castle was occupied by John D. Mahon and was valued at £62. It was still extant in the 1890s but is described as "in ruins" on the 1933 edition of 6" map. These ruins are still visible. OSI Ref:  M723223 Discovery map #47. OS Sheet #98.

Killagh:
Killagh More townland, Killallaghtan Civil Parish, Ballinasloe Poor Law Union, Barony Kilconnell:
Lands at Killaghmore and Clonecallin amounting to 635 acres were granted to Edmond Donnellan in 1684. Wilson refers to it as the seat of Mr. Donnellan in 1786. Stephen Donnellan was occupying the property at Killagh, valued at £33, at the time of Griffith's Valuation. In 1906 it was in the possession of Stephen J.R. Donnellan. It no longer exists.