Built from layers of timber, stone, peat, and brushwood, crannogs were typically occupied from the Bronze Age through to the early modern period, and they served as both practical dwellings and markers of status for the families who held them.

Garbally Demesne itself has a well-documented later history as the seat of the Trench family, the Earls of Clancarty, who developed the estate in the eighteenth and nineteenth centuries. The house and grounds passed through various hands and today the property is associated with a boarding school run by the Diocese of Clonfert. The crannog predates all of this by many centuries, a remnant of a much older pattern of settlement that the demesne landscape has quietly absorbed. Without more specific dating evidence or excavation records available in the public domain, it is difficult to say precisely when the island was constructed or who occupied it, but its presence in a demesne lake is not unusual. Landlord estates across Ireland frequently enclosed older archaeological features within their ornamental grounds, sometimes incorporating them into designed landscapes without any particular awareness of what they were.

The demesne sits just outside Ballinasloe, a town better known for its October horse fair than for its archaeology. The crannog itself is on private grounds, so access would require appropriate permission from whoever manages the estate.