Bastioned forts, with their angular projecting platforms designed to eliminate blind spots in defensive fire, were introduced to Ireland primarily during the sixteenth and seventeenth centuries, when European theories of fortification began to displace older medieval approaches to castle-building. Their presence on an island is itself telling; controlling waterways and island passages was a strategic priority during the Tudor and Cromwellian periods, when the west of Ireland was contested with considerable violence.

The fort on Inishmulclohy sits within a county that saw intense military activity during the Nine Years' War and its aftermath, and the broader Connacht landscape is scattered with fortifications, both Gaelic and colonial, from that era. Bastioned designs of this kind were typically associated with English crown forces seeking to consolidate control over territory, though Irish lords also adopted the form. Without more detailed records currently available for this specific site, the precise date of construction and the parties responsible for raising it remain unclear, which is itself part of what makes the place intriguing. An island fort, documented but not yet fully explained, occupying a stretch of water that most visitors to Sligo would never think to look toward.