Saint-Laurent Railway Bridge, Railway bridge in LaSalle, Canada

The Saint-Laurent Railway Bridge is a two-track steel truss bridge over the Saint Lawrence River, linking LaSalle in Montreal with Kahnawake. Two arched trusses meet above a central concrete pier, where a tall lattice tower rises; a straight truss section continues to a further pier on the right. Near its south end, twin vertical lift spans raise up to 21 metres for Seaway ships.

The original structure was completed in 1887 as a landmark railway connection for the region. A major reconstruction in 1913 reinforced it to handle heavier locomotives and growing freight demands.

The bridge carries the name Saint-Laurent, the French form of the river it crosses, and links the Montreal borough of LaSalle with the Kahnawake Mohawk Reserve on the south bank. Since the 2010s the exo commuter trains of the Candiac line (exo-4) have been its main users, while Canadian Pacific freight trains also cross it.

The bridge carries the exo-4 commuter line between Montreal and Candiac, so trains cross it on weekdays. The twin vertical lift spans stand just behind the south end, where the line meets the Saint Lawrence Seaway; ships pass beneath when the spans are raised. The parallel Pont Honoré-Mercier carries Route 138 and offers a road-level view of the steel trusses and the central lattice tower.

The first bridge's designer, Charles Shaler Smith, died in December 1886, before the structure opened in September 1887. He had used a continuous truss, a statically indeterminate form then rarely applied; Gustav Lindenthal took up the principle only in 1917 for the Sciotoville Bridge.