Beneath and around it, the River Shannon narrows at a point that people have been crossing, guarding, and fighting over for centuries, and the landscape on both banks still carries the evidence.

The current bridge is at least the third structure to occupy this stretch of the Shannon. The earliest known crossing here was built sometime between 1671 and 1690, though its precise location has never been established. It may lie beneath the riverbed, either preserved in silt or entirely removed when its mid-eighteenth-century replacement was constructed. That successor bridge was itself superseded by the present limestone structure in 1843. What makes the site unusual is not just this layering of bridges but the cluster of fortifications surrounding the crossing. On the Galway bank to the north stand a Martello tower, a type of squat circular defensive fort built in large numbers along Irish coasts and waterways during the Napoleonic period, and a late-medieval fortification known locally as Cromwell's Castle. On the Offaly bank to the south sits a bastioned fort, a more elaborate defensive form with projecting angular bastions designed to eliminate blind spots in cannon fire. Three distinct military structures, from different centuries and of different types, converging on a single river crossing, make it plain that controlling this point mattered enormously to successive powers. The Shannon here was not simply a geographical boundary between Connacht and Leinster; it was a bottleneck, and whoever held the bridge held the route.