The 270 acre island was granted to the Augustinian Canons from Clare Abbey in 1189 by Domnall Mór Ua Briain (Donald O'Brien), king of Thomond.

In 1393, a papal document describes the abbey as "so destroyed alike in respect of its buildings as of its books, chalices, and likewise of its temporal goods as to be threatened with ruin".

The monks continued to live on the island until it was attacked by Cromewellian forces in 1651.

[9] It is the largest of 25 small islands that span the crossing of the Shannon and Fergus estuaries.

[7] The remaining abbey buildings consist of a church with Romanesque windows, two adjoining chapels, a belfry, a cloister and a large square tower.