What looks like a straightforward urban crossing is in fact a structure built in several distinct phases across several centuries, its widened downstream face quietly recording the changing needs of a town that was itself stitched together from two separate medieval boroughs. The bridge connected Hightown, centred on Watergate Street, with Irishtown along Irishtown Street, and a crossing of some kind has been documented here from at least around 1207.

Archaeological investigation confirmed that the core of the present bridge dates to the 16th century, most likely tied to a recorded decision by the Corporation of Irishtown in 1568 to repair and build the bridge and the adjoining Town Wall. That structure was subsequently extended on its downstream side during the later 18th century, and then again by 5.7 metres in 1799. Upstream of the main crossing there is a detail that rewards closer attention: a freestanding arch keyed into the late medieval riverside wall on the south bank of the Breagagh. This arch is of late medieval date and aligns with the original Irishtown street-frontage, suggesting that when the bridge was widened and the road realigned in the 18th century, the arch was left stranded, its carriageway eventually removed and its purpose lost. A six-metre-high wall, supported on the bridge-arch and forming the western wall of a building that projected out over the river, was only taken down in 2003 as part of a flood relief scheme. Meanwhile, the remains of what was probably a gatehouse are thought to survive beneath the 18th-century building at No. 6 Watergate Street, just to the west of the bridge's southern end. Excavations at that address also uncovered a stretch of 15th or 16th-century town wall on the south bank, likely contemporary with both the bridge and the gatehouse, adding another layer to a site where the medieval street plan and its defences are still, in places, only just below the surface.