Mullinalaghta formed part of the medieval territory of Annaly, largely corresponding to today's County Longford. It was under the control of the "Mac Gearadháin" (Gaynor) family, being referred to in sixteenth century documents as Muntergerran ("Muintir Gearadháin"). Ecclesiastically, it was under the control of the abbey of Inchmore in Lough Gowna, founded by Saint Colmcille in the 6th century. This was reflected by Mullinalaghta forming part of the civil parish of Columbkille and also being part of the same Roman Catholic parish until 1839, when it was joined with the Cavan parish of Scrabby to its north, with which it has since been united. The area has been hard hit by emigration, with the population declining from a pre-Famine peak of over 3,200, to its present population of less than five hundred.