Killallaghtan lies in the eastern part of the civil parish of Killallaghtan barony of Clonmacnowen/Cloonmacnoon Co Galway. It is bounded in this parish by Ballynamuddagh and Tooreenard townlands in the said barony and by Gurteenawillen in the barony of Kilconnel and in Aughrim parish by Oatfield.
O’Donovan’s Field Name Books give other spellings of this townland: Cill Dha Lachtnain, Killalloghtan, Killalerton and Killaghtan.
Down Survey map shows under the name ‘Killaghmore’ Richard Martin, a catholic owned this land in 1641. It was owned by Edmund Donnellan, a protestant in 1670. It states there were 201 plantation acres of unprofitable land, 379 plantation acres of profitable land and 379 plantation acres of forfeited land.
The census from 1901and 1911 give no information on who lived in this townland at that time.