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This 2006 photo shows the Honore Mercier Bridge (QC 138) looking south from the LaSalle borough of Montreal. Note the raised profile of the truss span over the St. Lawrence Seaway relative to the much longer arch span. (Photo by Laura Siggia Anderson.)

A NEW HIGHWAY CROSSING FOR THE SOUTH SHORE: As early as 1910, officials on the South Shore sought a new automobile crossing to supplement the existing Saint Laurent Railway Bridge between the city of LaSalle on the North Shore (now a borough of Montreal) and the Kanhawake Indian Reservation (then called Caughnawaga) on the South Shore. Denied permission to attach outboard roadways by the Canadian Pacific, which owned the bridge, local officials lobbied the province to build an automobile-only span.

Honore Mercier, the provincial minister of lands and forests and a representative from Chateauguay, expressed concern about the absence of a vehicular connection and the lack of a provincial commitment to build such a span:

There has been agitation for some time for a roadway bridge across the St. Lawrence to parallel the (Canadian Pacific Railroad) bridge, which now runs from Highlands towards Adirondack Junction. There have been petitions from various municipalities, setting forth the need for a link at this point, suggesting Caughnawaga and Ville LaSalle, as the best terminal points.

For a while there was the idea of obtaining from the (Canadian Pacific Railroad) permission to add a roadway to the already existing bridge. This, however, seems to have fallen through, and the new commission will be called on to devise ways and means for the erection of a separate structure, and the financing of the work. The Government is not pledged at the present time to any subscription towards the bridge, and its subsequent action will depend largely on the findings of the commission, the members of which will be appointed by the Lieutenant-General-in-Council, and will probably be chosen from among the citizens of the interested municipalities, backed by the necessary technical advisers.

After studies were conducted in the spring and summer of 1928, the Quebec Department of Public Works determined in a report released that October that a new fixed automobile crossing between LaSalle and Kahnawake would cost C$1.8 million, less than the C$2.3 million it would have cost to add roadways to the Saint Laurent Railway Bridge (as was done with the Victoria Bridge [QC 112]). Under the auto-only bridge option, the province would retain ownership of the bridge, while under the railway bridge option, the Canadian Pacific Railroad would have kept ownership of the bridge.

After studies were conducted in the spring and summer of 1928, the Quebec Department of Public Works determined in a report released that October that a new fixed automobile crossing between LaSalle and Kahnawake would cost C$1.8 million, less than the C$2.3 million it would have cost to add roadways to the Saint Laurent Railway Bridge (as was done with the Victoria Bridge [QC 112]). Under the auto-only bridge option, the province would retain ownership of the bridge, while under the railway bridge option, the Canadian Pacific Railroad would have kept ownership of the bridge.

The bridge proposal languished for four years as financing the bridge was a concern. Although the province was to pay most of the construction cost, the federal government also was to provide financing because the southern terminus of the bridge was within the Kanhawake Indian Reservation. With the federal government bearing part of the cost, some ministers in the House of Commons objected to the use of tolls, which was the policy of the Quebec government. As the Great Depression began, however, the bridge was seen as an important catalyst for construction jobs, and ultimately the federal government included the bridge under its jobs program.

On November 14, 1932, the LaSalle-Caughnawaga Bridge Commission, which later was known as "The Corporation of Lake St. Louis Bridge Commissioners" (as described on the original dedication plaque on the bridge) awarded contracts to the Dominion Bridge Company. Initial construction began almost immediately.

This vintage postcard shows the Honore Mercier Bridge as originally built. Note the single-span arch bridge and the gently-sloping southern approach to the right of the span. The southern approach was rebuilt in the late 1950s, while the main river span was twinned in the early 1960s. (Postcard from Evelyn Theriault's "A Canadian Family" site.

DESIGN AND CONSTRUCTION OF THE ORIGINAL BRIDGE: The original bridge was comprised of 12 spans totaling 889 meters (2,918 feet) in length: the main 122-meter-long (400-foot-long) steel-arch span, two side spans flanking the steel arch span; and nine through-truss spans of varying length extending north from the steel arch superstructure to the LaSalle shoreline. There was a single 8.1-meter-wide (26.5-foot-wide) roadway to accommodate two lanes of vehicular traffic (one in each direction), flanking by a 1.2-meter-wide (four-foot-wide) walkway.

On the north end of the bridge was a 91-meter-long (300-foot-long), five-span viaduct connecting to the street network in LaSalle; this approach was built with a 3.5% approach grade. Connecting to the South Shore was a 381-meter-long (1,250-foot-long), 14-span viaduct connected to an improved highway (now part of QC 132); this approach was built with a 2.5% grade.

With engineers and ironworkers--many of whom came from the Mohawk tribe in Kahnawake--working around the clock, the piers were completed in only nine months. However, the speed of the work concealed the complexity of construction. The deep, swift waters of the St. Lawrence--the water was more than 12 meters (40 feet) deep--and rock with a thick layer of glacial clay necessitated construction of pneumatic caissons rather than conventional cofferdams for the construction of the piers. The size of the two caissons were so large (9.75 meters by 22 meters, or 32 feet by 72 feet) that they were assembled by Dominion Bridge at its factory on the Lachine Canal and floated by barge to the construction site. Because of the swift currents, the caissons had to be secured by cables attached to the barges until they were settled in their final position.

Work on the steel superstructure began in August 1933. More than 4,000 tons of structural steel were used in this part of the project. As completion neared--with a deadline of May 1, 1935--an average of 71.6 meters (235 feet) of new concrete was poured each day onto the roadway. New "French Habitant"-style stone-and-concrete tollbooths, at which a 50-cent-toll was to be collected, were built at each end of the bridge.

The new C$3 million bridge was opened to traffic on June 22, 1934, cutting the average distance between LaSalle and Kahnawake by 26 kilometers (16 miles). It was dedicated formally on July 11, 1934 and named in honor of Mercier, who had championed the cause of the bridge in the 1920s. In addition to city and provincial officials, Montreal's Roman Catholic and Anglican bishops blessed the structure, as was common for public works dedications in the province until the 1960s. Members of the Iroquois tribe from Kahnawake also participated in the ceremonies.

The Corporation of Lake St. Louis Bridge Commissioners owned and operated the Mercier Bridge until April 30, 1944, when the provincial government took over the span. Upon transfer of the bridge to the province, tolls were removed from the span.

This 2008 photo shows the westbound / southbound Honore Mercier Bridge (QC 138) approaching the steel arch span over the main St. Lawrence River. (Photo by Doug Kerr,

RAISING THE BRIDGE FOR THE SEAWAY: On September 22, 1954, the federal government announced plans to build a new southern approach to the Mercier Bridge to accommodate the St. Lawrence Seaway, which was in its early stages of construction along the South Shore. Instead of building a lift span as some officials had suggested, the federal government, as part of its takeover of the southern half of the Mercier Bridge (the northern half was to remain under Quebec jurisdiction) proposed eliminating the low-level viaduct approach to Kahnawake and building a high-level Warren truss bridge over the Seaway. At the same time, the project would add a second roadway over the Seaway, with the provision for future expansion north of the Seaway.

The federal government awarded contracts in August 1956 and January 1957 for the project, which included construction of a two-lane temporary span and a new multi-level interchange with QC 132 in Kahnawake. In May 1957, workers demolished the 14 spans of the old southern approach.

For the new southern approach, workers erected 30 single piers, 15 dual-width piers, and two abutments ranging in height from 14.5 to 31.6 meters (47.5 to 103.8 feet). The vertical clearance of the Warren truss span over the St. Lawrence Seaway was to be 38.7 meters (127 feet)--which exceeded the 27-meter (90-foot) vertical clearance of the steel arch span over the main river--while the distance between piers was to be 92 meters (302 feet). New "hammerhead" piers were used in the construction of the ramp system connecting the bridge with Kahnawake and Chateauguay. The new high-level span and approaches were opened to traffic in August 1958, 10 months before completion of the St. Lawrence Seaway.

A CLOSE CALL: On October 12, 1959, a barge filled with explosives in the St. Lawrence River lost control near the Beauharnois Locks, threatening the St. Lawrence Seaway, the St. Laurent Railway Bridge, and the Mercier Bridge. The barge ran aground near Pointe-Claire, but not before all highway and rail traffic on the two bridges was halted for several hours.

TWINNING THE MERCIER: In March 1961, the Ministère de la Voirie du Québec (MVQ) began work on a C$25 million expansion of the northern half of the bridge over which the province had jurisdiction, including construction of an expressway connection to A-20 (Autoroute des Souvenirs) through LaSalle. The project entailed construction of a new parallel steel arch bridge and multi-span through-truss approach for what was to become the northbound lanes. The new northbound span was to diverge from the original southbound span as it approached the LaSalle shoreline.

Upon the opening of the parallel span on August 15, 1963, all traffic was diverted onto the new span while the MVQ closed the old span--what eventually became the bridge's southbound lanes--for rehabilitating and strengthening the steel superstructure, as well as upgrading the bridge's electrical system. Both bridges reopened for four-lane operation on August 14, 1964, about three weeks ahead of schedule. However, the Mercier Autoroute connection between the Airlie Street (the former northern terminus of the bridge approach) and A-20 did not open until 1966, one year behind schedule.

This 2008 photo shows the westbound / southbound Honore Mercier Bridge (QC 138) approaching the high-level Warren truss span over the St. Lawrence Seaway. (Photo by Doug Kerr,

THE BRIDGE'S ROLE IN THE OKA CRISIS: For a seven-week period in the summer of 1990, members of the Mohawk tribe in Kahnawake seized control and barricaded the Mercier Bridge in sympathy with their fellow Mohawk members in the Kanesatake Reservation, whose protest of a golf course expansion in Oka led to a shooting match and the death of a Quebec Provincial Police (Surete du Quebec) officer. The 55,000 commuters who used the Mercier Bridge each day had to take a lengthy detour to the already congested Champlain Bridge (A-10, A-15, and A-20), and the two-hour commutes that resulted further strained relations between Chateauguay and Kahnawake residents.

The bridge reopened toward the end of the Oka crisis in September 1990 after minor repairs. Although tensions have subsided, the span was the site of peaceful protests that closed the bridge for a few hours in 2006 and 2007, when members of the Mohawk tribe hoisted "warrior" and "confederacy" flags atop the bridge. (The flags were replaced hours later by Quebec flags just days after the 2006 protest.)

REBUILDING THE MERCIER BRIDGE: In 2006, the Jacques Cartier and Champlain Bridges Incorporated (JCCBI), which has overseen the federally-controlled section of the bridge since 1978, and the Ministère des Transports du Québec (MTQ) announced plans for a C$166 million overhaul of the Mercier Bridge, the largest such bridge reconstruction in Canadian history. The federal-provincial joint managers enlisted the help of the Kanhawake Mohawk Council to minimize disruption, and reached a contract with the Mohawk Bridge Consortium for major construction work. The work is expected to extend the life of the bridge by 75 years.

The first phase of the project entails rehabilitating and redecking the three elevated ramps that comprise the bridge's southern approach. The ramps are being built as follows:

  • Ramp 2 (Mercier-LaPrairie ramps): This is the four-lane ramp connecting the bridge with QC 132. Capacity was reduced to two lanes--one in each direction--while work continued on replacing one roadway at a time. The Ramp 2 sub-project was completed in November 2010.

  • Ramp 3 (Mercier to Chateauguary ramp): This ramp carries westbound / southbound QC 138 traffic from the bridge toward Chateauguay. Work on this sub-project, which began in March 2010, entails removing one section of the ramp at a time during the overnight hours and reopening the ramp for the morning rush hour. Once the roadway is replaced, workers will return to add a new multi-use path for pedestrians and cyclists. This sub-project is scheduled for completion in 2011.

  • Ramp 4 (Chateauguay to Mercier ramp): This ramp carries eastbound / northbound QC 138 traffic from Chateauguay toward the bridge. This part of the required a complete closure, but a temporary roadway--complete with signals--was part to handle this traffic, which was rerouted onto Ramp 2. The Ramp 4 sub-project was completed in November 2009.

The second phase of the project, which is slated to begin in 2011 and expected to continue through the fall of 2014, entails the replacement of the concrete deck on both the federally-owned and provincially-owned sections of the bridge. A new multi-use trail will replace the existing sidewalk along the southbound lanes of the bridge. In both phases of reconstruction, more than 1,300 concrete panels covering 40,684 square meters (437,919 square feet) will be used.

According to the MTQ, the Mercier Bridge carries approximately 80,000 vehicles per day (AADT). Trucks comprise only 5% of total bridge traffic; this is lower than the 20%-25% at the other major Montreal-area crossings because of the lack of a direct autoroute connection at the southern approach.

This 2008 photo shows the eastbound / northbound Honore Mercier Bridge (QC 138) approaching the steel arch span. The two roadways diverge at the steel arch spans and do not rejoin each other until EXIT 1 (Airlie Street / Newman Boulevard) on the Mercier Autoroute in LaSalle. (Photo by Scott Steeves,

PART OF A NEWLY EXTENDED A-13: The A-13 designation should be extended south along the Mercier Autoroute and Mercier Bridge (QC 138) south to Kahnawake, then east along the present route of QC 132 to the stub end of the current A-30, replacing the A-730 now proposed for the stub. Service roads would be built along the present alignment of QC 132 to serve homes and businesses in the Kahnawake Reservation. Although this project could be done with a minimal amount of displacement, it is unlikely this project ever would be undertaken given the history of tensions in the area.

Type of bridge
Construction started
Opened to traffic
Parallel span opened to traffic
Length of main steel arch span
Length of main Seaway truss span
Length, abutment to abutment
Width of each roadway
Number of traffic lanes
Clearance at center above mean high water
Deepest foundation below mean high water
Foundation type
Cost of original structure
Cost of parallel structure and reconstruction

Steel arch and through truss
November 14, 1932
June 22, 1934
August 15, 1963
121.9 meters (400 feet)
92.1 meters (302 feet)
1,361.8 meters (4,468 feet)
8.1 meters (26.5 feet)
4 lanes
36.6 meters (120 feet)
21.6 meters (71 feet)

SOURCES: "Farm Credits Act Is Enacted by Legislature," The Montreal Gazette (3/20/1928); "New Caughnawaga Bridge Is Assured," The Montreal Gazette (10/16/1928); "Bridge Bill Is Held in House," The Ottawa Citizen (5/30/1930); "Order for Dominion Bridge Looms on Horizon," The Financial Post (1/23/1932); "Bridge Work Advanced," The Montreal Gazette (8/23/1933); "Bridge Roadway Is Near Completion," The Montreal Gazette (5/12/1934); "New River Bridge Opened to Traffic," The Montreal Gazette (6/23/1934); "Colorful Scenes As Caughnawaga Span Inaugurated," The Montreal Gazette (7/12/1934); "New St. Lawrence Bridge Opened," The New York Times (7/12/1934);"Quebec Takes Over Toll Bridge Firm," The Montreal Gazette (5/01/1944); "Assured--But Not Told" (Op-Ed), The Montreal Gazette (11/03/1954); "Mercier Bridge Contracts Awarded," The News and Eastern Townships Advocate (8/30/1956); "Mercier Bridge Contract Awarded," The News and Eastern Townships Advocate (1/17/1957); "Bridge Approach Blasted" by Clayton Sinclair, The Montreal Gazette (5/09/1957); "Indians Lose Dispute with Seaway," The Ottawa Citizen (3/09/1957); "Constant Flow of Concrete Raises Piers for New High Approach to Mercier Bridge," The News and Eastern Townships Advocate (9/05/1957); "Steel Rises on Mercier Bridge Approach," The Montreal Gazette (1/01/1958); "Mercier Bridge Rebuilding," The Montreal Gazette (1/21/1958); "Traffic Snarl 'Worst'," The Montreal Gazette (7/14/1958); "Montreal Bridges Periled as an Explosives-Laden Barge Runs Wild in Lake," The Lewiston Daily Sun (10/13/1959); "New Approach for Mercier Bridge" by Don Johnson, The Montreal Gazette (7/31/1962); "Mercier Span To Be Ready by Labor Day" by Gordon Pape, The Montreal Gazette (7/07/1964); "Deluxe Traffic Jam Marks Reopening of Old Mercier Span" by Roger Bird, The Montreal Gazette (8/15/1964); "Dream Highways Soon a Reality," The Montreal Gazette (5/15/1965); "Jetport Link Alternate Proposed," The Montreal Gazette (9/14/1972); "Fury Rising in Quebec Over Mohawk Standoff" by John F. Burns, The New York Times (7/22/1990); "Barriers Are Down in Mohawk Dispute in Quebec," The New York Times (8/30/1990); "Quebec Bridge Mends, But a Town Is Scarred" by Chris Hedges, The New York Times (9/05/1990); "Two Lanes Open During Mercier Bridge Construction" by James Mennie, The Montreal Gazette (6/16/2008); "Bridges Between Montreal and South Shore Carry 86 Million Cars a Year," CBC News (1/09/2009); "A Bridge Too Dilapidated: Mercier Is a Third World Span" by Max Harrold, The Montreal Gazette (4/07/2009); Federal Bridge Corporation; Jacques Cartier and Champlain Bridges Incorporated; Ministère des Transports du Québec; Transport Canada; Christine Donais; Evelyn Theriault.

  • QC 138 and A-13 shields by Wikipedia.
  • Lightpost photos by Douglas Kerr.




  • Mercier Autoroute (QC 138)
  • Autoroute des Souvenirs / Veterans Memorial Autoroute (A-20)
  • Autoroute de l'Acier / South Shore Autoroute (A-30)

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