The CNoR acquired, at an “advantageous” price (never disclosed), a parcel of land covered with “second-rate buildings”, at de la Gauchetière and McGill College Streets, on which it built a terminal that was supposed to be temporary. Sir William Mackenzie and Sir Donald Mann of the CNoR had ambitious development plans for the area around the terminal, but they would not come to fruition for almost 50 years, and then not exactly as Mackenzie and Mann had planned.

The tunnel is about 3 miles (5 km) long, has a 0.6% grade against outbound trains, and is not forced-air ventilated. From the start, it was proposed that only electric trains should ever operate in the tunnel. The CNoR chose a 2400-volt DC system, like the Butte, Anaconda, and Pacific (BA&P) copper-hauling railway in Montana; and established an engine change point at Lazard (Val Royal 1926-1995, now Bois Franc), where electrics were changed for steam locomotives, or vice versa, on mainline trains to or from Toronto and Ottawa. CNoR also built shops for their electric locomotives at Lazard, along with a loop track for turning locomotive-hauled trains.

1911 Incorporation of Canadian Northern Tunnel and Terminal Company, later renamed Mount Royal Tunnel and Terminal Company, as a subsidiary of CNoR, to build the tunnel and terminal.
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1912 July 8 Start of construction, at West Portal, near present Canora (formerly Portal Heights) station. Total cost of project was $10 million in 1918 dollars; almost $111 million today

1913 December 10 Tunnelling crews from east (downtown) and west portals met in the centre of the tunnel; alignment was off by only about one inch. Concreting of tunnel was completed by 1916; tracks and catenary were installed by September 1918. Slow progress was due to World War I and CNoR’s financial difficulty.

1914 Order placed with General Electric (GE) for 6 boxcab electric locomotives, like Butte Aanaconda & Pacific units. Née CNoR 600-605, then CN class Z-1a 9100-9105, then 100-105, finally 6710-6715. Units 600-603 were built entirely at Schenectady, New York; 604 was built in Toronto, from parts shipped there from Schenectady; 605 was built entirely at Peterborough, Ontario. Delivery delayed until 1916-1917 due to war. 603 was retired in 1993 as CN 6713, all others remained in service until June 2, 1995.

1914 Six electric multiple unit (MU) cars were ordered from Pressed Steel Car Co. for commuter service. This order was later cancelled; former Grand Trunk Pacific coaches 2012 and 2015 were converted to electric MU motor cars, 15903 and 15904, in 1925.

1917 December 20 Bankruptcy of CNoR; in 1919, it became part of the Canadian Government Railways, which in turn became part of Canadian National Railways (CN) in 1923. Mackenzie and Mann’s redevelopment plans for the area around the terminal were frustrated.

1918 October 21 Unit 601 hauled the first train from the terminal into tunnel. Opening was little noticed; a flu epidemic resulted in a ban on large public gatherings, and World War I was still underway. Regular commuter service began to Lazard, about 7 miles.

1921 February 27 Electrification extended about one mile north from Lazard to Cartierville.

1925 July Electrification extended about 9 miles west from Lazard to St. Eustache-sur-le-Lac (Deux-Montagnes since 1963, now Grand-Moulin); this is still the main line today.

1927 CN President Sir Henry Thornton proposed another ambitious redevelopment plan for the area around the Tunnel Terminal; also frustrated, by Great Depression of 1929. A tentative start on a new downtown station was halted by 1931; restarted in 1938.

1941 December CN acquired 9 English Electric (EE) boxcab electric locomotives from the National Harbors Board Railway (also electrified at 2400 volts DC) in exchange for 7 steam switchers. The actual date is not certain - the steam locomotives were transferred to the NHB in December 1941 (Corley and Clegg - Canadian National Steam Power) and it is assumed that the electrics came to CN at about the same time - more information would be welcome.  Built in 1924-1926, by Beyer Peacock (mechanical part) and Dick Kerr Works of EE (electrical part). Née NHB 101-109, then CN class Z-4a 9180-9188, then 180-188, finally 6716-6724. Only 4 units lasted until June 2, 1995: 6716, 6722, 6723, and 6724.

1943 July 14  CN opened present Central Station, combining in one location 3 of its widely scattered “legacy” stations (CNoR Tunnel Terminal and Moreau Street, and GT Bonaventure). The old “temporary” Tunnel Terminal was closed the next day, and demolished in January 1952; the present CN Headquarters building was opened on that site in 1961.

1943 Three engine change points were established: at Gohier, near Eastern Junction, for trains to or from northern Quebec; at Turcot Yard, for trains to or from Ottawa and Toronto; and Bridge Street, at the north end of the Victoria Bridge, for trains to or from the South Shore.

1943 Construction of the l’Assomption (later Longue Pointe, then Joliette, now St. Laurent) Subdivision across northeastern part of Montreal Island; crosses Mount Royal Subdivision at Eastern Junction (EJ Tower located in southwest quadrant). Electrification started 1945-46 to Montreal North station, at Lacordaire Boulevard, about 6 miles east of Eastern Junction.

1946 January 12 NW2 #7903, hauling 2 burning coaches out of Central Station, collided with oil-electric motor car 15819, near South Portal of tunnel; 4 killed. Tunnel was closed for 10 days. Smoke was a major factor in the accident; electric-only order for tunnel was reinforced.

1946  Electrified service started to Montreal North; never more than one locomotive-hauled rush hour round trip.

1947 Retirement of first-generation MU motor cars 15903 and 15904; scrapped 1949.

1950, July 28 Delivery of 3 GE steeple cab electric locomotives, built at Erie, Pennsylvania, class Z-5a, née 200-202, later 6725-6727. These units were the line’s “hot rods”; they were preferred for hauler service because of their fast acceleration. All 3 units lasted until June 2, 1995.

1952 Delivery of 18 electric MU cars from Canadian Car and Foundry (CCF), with GE electrical equipment: 6 motor cars, class EP-59a, née M-1 to M-6, later 6730-6735; and 12 control trailers, class ET-69a, née T-1 to T-12, later 6739-6749. These cars were the line’s workhorses for the next 43 years. Normal consist was one motor car and 2 trailers (sometimes only one trailer); they could be coupled in trains of up to 9 cars. Motor cars always led outbound trains from Central Station. All but 4 cars lasted until June 2, 1995.

1954 GE and EE boxcabs retrofitted with same GE754 traction motors and other electrical equipment as steeplecabs and MU motor cars.

Late 1950s Start of building boom in downtown Montreal, on air rights over CN tracks, that eventually covered up the tunnel’s South Portal, and the tracks leading to it. Until then, the area was a large open cut called “the hole”; from the Dorchester (now René-Lévesque) Boulevard bridge, one could see the action. Among the large buildings erected in this period: the Queen Elizabeth (Reine-Élisabeth) Hotel, opened 1958; CN HQ (1961); and Place Ville-Marie (1962).
Increasing use of diesels on main line trains eliminated the need for engine changes before entering Central Station. Use of electrics was reduced; catenary to Turcot was removed.

1960 July 23  Roxboro station MU trailer car T-8, leading a 3-car eastbound train to Montreal, collided head-on with westbound freight train (RS-18 #3852 leading). One passenger, a 22-year- old woman, was killed in the wreck; 70 others were injured; T-8 was scrapped that summer.  Investigation found that all 4 crew members of the commuter train overlooked an order to meet the freight train at Des Prairies siding in Laval ; all were dismissed after the accident.

Early 1960s  First of many proposals to modernize the line; this one proposed converting it to Metro line 3. In 1962, after Montreal was awarded Expo 67, this plan was sidetracked in favor of Line 4 (to Ile Ste Hélène and Longueuil) and never revived.

1968, November 8 Last train to Montreal North; Metro line 2, opened 14 October 1966, bled off most of its traffic (probably never high to start with). Sauvé Metro station is near CN Ahuntsic station, still standing today and used by VIA trains. Catenary removed from Montreal North line, except for a short connection at Eastern Junction, used by locomotives hauling mainline trains (locomotive-hauled and RDC) through tunnel until the early 1990s.

1969 Final numbering scheme (67xx) of DC rolling stock adopted.

1971, May 15  CN filed application to then-Canadian Transport Commission to abandon line, claiming it was uneconomic; 65 to 75% of operating revenues went to pay wages.

  1971, November 4  4 EE locomotives 6718-6721 retired; they had been out of service since about 1967, and cannibalized for parts for others.

1974, October 7  A-ma-Baie station Eastbound freight train (RS-18 #3701 leading) collided head-on with westbound diesel hauled passenger train (GP9 #4107 leading) to Grenville; 2 crewmen on 4107 killed.

1976 Cartierville service was reduced to rush-hour only; service to Deux-Montagnes cut sharply, from 44 trains per weekday in 1966 to 18 by 1979. Until 1975, weekday daytime service was hourly on each branch, or every 30 minutes from Central Station to Val Royal. Over the next 5 years, CN repeatedly threatened abandonment unless the line was modernized and government assistance was forthcoming. Another modernization plan (1981) went nowhere.

Early 1980s  Catenary voltage increased from 2400 to 3000 volts DC.

Early 1980s  MU motor car 6732 destroyed by fire, when and where unknown; scrapped 1985.

1982 July 1 10-year operating agreement with then Commission, now Société de transport de la Communauté urbaine de Montréal (STCUM)took effect; CN operated the line under contract to STCUM. Cartierville service abandoned; most trains to Deux-Montagnes restored (from 18 to 28 trains per weekday). Within MUC (Central Station - Roxboro, corresponding to present zones 1 and 2) fare integration with Metro and STCUM buses was adopted; fare anywhere within the MUC was 2 bus and Metro tickets, but transfers to and from Metro and STCUM buses permitted.

1986 January 1 Fare reduction: from Central Station to Val Royal (corresponding to present zone 1) now equal to single bus and Metro fare.

1989 Cartierville branch cut back to a 300-foot stub at Val Royal, used to short-turn MU trains.

Late 1980s/Early 1990s  Last major rebuild of DC rolling stock, including:
 - MU cars, side sills severely corroded; new sills added. Trailer 6748 was too badly corroded to rebuild; retired, stripped of structural parts for its sisters.
- Cabs on one end of each GE and EE boxcab locomotive. From then on, units were usually coupled back-to-back at the non-rebuilt ends.
- Truck frames of EE units 6716, 6722, 6723, and 6724; out of service from December 1991 to June 1992. 6717 retired, cannibalized for parts for others.
CN set 1992 deadline for abandonment unless modernization got on track.

1992 February 12 Quebec Transport Minister Sam Elkas announced a $289M modernization of the line: 58 new cars ($130M contract awarded to Bombardier); electrification to be changed to AC (25,000 volts, 60 Hz); stations to be renovated; tracks and signal system to be rebuilt; a short extension, to Autoroute 640 in Deux-Montagnes, to be added.

1992 - CN leased 35 CCF-built coaches (ex-CN, 1954) from VIA Rail, to replace worn-out 1920s heavyweight coaches; added openable windows for ventilation. Rebuilt GP9RM diesels hauled the longest and heaviest trains, to ease the load on electric locomotives, especially in winter; however, electrics still hauled trains through the tunnel, cutting off at Portal Heights. Inbound trains (diesel or electric) coasted downhill through tunnel.

1992 - ? August 2: Weekday service cut from 16 to 12 trains, to help conserve MU cars.

1993, 1994, and 1995, summers Line closed completely for various phases of modernization, as described later. Service was curtailed progressively before shutdown, and restored in stages after work completed. Trains were replaced with various bus services for the duration of the work.

1993 Retirement of GE boxcab 6713, EE boxcab 6717, and MU trailer car 6748.

1994 Fall  First deliveries of new cars, built by Bombardier with GE electrical equipment. Cars are stored at a new shop in St. Eustache, north of Autoroute 640, off Boulevard Albert-Mondou, still used today. Test runs were made over a short section of track (25 kV 60 Hz) running south from the shop to a point just north of Oka Road overpass, where DC catenary ended. A short gap in the catenary separated AC and DC systems.
- MU motor car 6731 damaged by fire at Deux-Montagnes; retired, probably scrapped.

1995 February Removal of old DC catenary south of Central Station, leading to former CN Pointe St. Charles shops (later AMF Technotransport, now Alstom). Maintenance was moved in 1943 to “the Pointe”, then in 1985 to Central Station (old Turbo train maintenance bay). New AC catenary later erected to Cape (mile 0, Deux-Montagnes Subdivision).

1995 May 1 Catenary cut back from Deux-Montagnes to Laval-sur-le-Lac, to allow work in the Deux- Montagnes area.

1995 June 2 End of the line for the “rolling museum”: Last run of old DC rolling stock.
Train 951 left Central Station for Laval-sur-le-Lac at 6:30 PM. Consist was GE boxcabs 6711 and 6710 (née CNoR 601 and 600 respectively), with engineer Ken Wadden, and CN coaches 5064, 5062, 5063, 5065, and 5070 (last “Canadian Flyers”, CCF, 1942). The locomotives carried a commemorative plaque, which the Canadian Railway Museum had specially made up for the occasion. Based on the old CNoR logo, with 2 dovetailed wedges in a circle, it showed dates of first and last runs, 21-10-1918, and 02-06-1995. Several BRS members were either aboard or at trackside. Train returned to Central Station as #952, with 6710 leading, at about 8:40 PM; after final photo session, locomotives and power killed for the last time. CN-owned rolling stock was then moved to Taschereau Yard; leased VIA coaches were returned to VIA.

1995 June 5 Val Royal station was demolished, after being vandalized over the weekend.

1995 Summer and Fall
- Final phase of renovation work completed, as described later.
- Disposition of DC rolling stock, as described later.

1995 October 26  Line reopened for rush-hour revenue service, after several delays. Rush-hour service was originally to resume August 28, and full-time service September 18.The new trains were an immediate hit with passengers, who were fed up with breakdowns and either roasting or freezing in the old trains. At first, the only apparent problems were with the end doors on some cars not closing properly. Bombardier technicians rode shotgun on some trips, to fix any problems. Full service resumed December 1, after completion of fencing along the line.

1995 December  First serious problems appeared; during a major snow storm, melted snow shorted out traction motors. Service suspended 20 December to 08 January 1996 while all 116 motors (4 for each of the 29 motor cars) were sent back to GE at Erie, Pennsylvania, for re-insulation. Trains have operated reliably ever since. (This was not a new problem: In February 1958, the same problem affected the Pennsylvania Railroad’s GG1 electric locomotives, built in the 1930s and 1940s;  at one point, almost all 139 of them were out of service).

1996 January 1 Newly-created Agence métropolitaine de transport (AMT) became operator of the line, and owner of rolling stock (effective December 20), replacing STCUM.

1997 Installation of 2 small high platforms, one with a shelter, at Roxboro-Pierrefonds station, for wheelchair access. “Switchback” ramps give access from main (low) platform. Centre (high- level) door of the first car of a Montreal-bound train lines up with this platform; signs indicate proper stopping positions for various train lengths, from 2 to 10 cars. Bridge plate slides and lowers into place, to close gap between platform and sill of car door. At Central Station, this car stops near elevator to concourse; a portable bridge plate is used there. The Quebec government is considering whether to install these platforms at other stations; so far, there are no plans to do so

  1998 January 6 Ice storm prevented trains from operating; doors of trains were frozen shut, they could not leave St. Eustache yard. Power system and catenary were unaffected.

2000 Municipal building housing new Deux-Montagnes station named Édifice Jean-Guy Bergeron Building, in honor of former Deux-Montagnes Mayor and MNA, who worked for modernization of line.

2001 January 1 Fare zone boundary moved; Du Ruisseau and Bois-Franc stations transferred from fare zone 1 to zone 2.

2003 January 1 Monthly and weekly bus and Metro passes issued by Montreal transit system, now called Société de transport de Montréal (STM), no longer accepted aboard trains.