GO Transit started on May 23, 1967, running single-deck trains powered by diesel locomotives in push-pull configuration on a single rail line along Lake Ontario's shoreline.

[5][6] When GO trains began operation, they ran on tracks mostly owned the two major freight railways of Canada: Canadian National (CN) and CPKC.

[7] in 1988, a small but significant milestone in network growth occurred when it expanded its Lakeshore East line on new track it built by itself.

After the YDHR went bankrupt in January of 2024[citation needed], Uxbridge considered extending rail operations.

[20] The Milton line is owned and operated by Canadian Pacific Kansas City which has restricted the number of passenger trains, only allowing for one-way service.

[21] A long-proposed solution to allow access for passenger trains on the Midtown line is a re-routing of CPKC freight traffic known as the "Missing Link".

[22] The Missing Link is considered an ambitious project, requiring negotiations between both CPKC and CN, who own the Halton subdivision.

[23] In 2024, the Progressive Conservative Party announced plans to build the Missing Link to free up both the Milton and Kitchener line.

Hydrogen fuel cells were studied as an alternative to rail electrification but ultimately were deemed unfeasible.

[25] In 2022, the Ontario government under premier Doug Ford began the first phase of electrification, with plans to electrify 600 kilometres of track and an estimated finish date of 2032.

[26] GO Transit rail service to Bolton was first proposed by the Ontario government under the MoveOntario 2020 plan in June 2007.

Metrolinx determined that the projected ridership did not justify the costs, and downgraded the Bolton line from the 15- to the 25-year plan on February 14, 2013, when amendments were made to The Big Move.

[29][30] In 2025, as part of a campaign promise, the Progressive Conservative Party under Doug Ford announced plans to create the Bolton line.

[31] However, the Havelock line was moved to the 25-year plan on February 14, 2013, because of "very modest ridership potential and significant infrastructure and operational challenges related to the Agincourt rail yards.

The potential to provide commuter rail service to Peterborough was noted by GO Transit in its 2020 strategic plan, and was also included in The Big Move.

Once reaching Toronto, three different routes were explored through the east end, to deal with the same "significant infrastructure and operational challenges related to the Agincourt rail yards" that complicate GO's Havelock line.

[35] In 2024, the Progressive Conservative Party announced plans to build the Missing Link[22], and in 2025 as part of a campaign promise the Progressive Conservative Party announced plans to create the Midtown Line, spanning from Streetsville GO Station in the east to Caledon in the west.

Reports have forecasted a ridership of over 500,000 by 2041, and would cut travel time between Cambridge and Union Station to 87 minutes.

Another guard-like staff member, the Customer Service Ambassador (CSA), is located in the accessibility coach, which is the fifth car from the locomotive.

The CSA is responsible for opening and closing the train doors, making announcements over the PA system, and acts as the first responder in case of an emergency on board.

When a train arrives at a station, the CSA puts a small accessibility bridge across the gap between the platform and the doorway.

GO Transit inspects train air conditioning more frequently during summer, as A/C systems have to work harder on hot days.

The F59PH was also the first series of locomotives used by GO Transit that feature dynamic braking, the effectiveness of which was greatly increased to as low as 8 km/h.

[56] In 2005, GO Transit contracted with MotivePower to build 27 MP40PH-3C units in order to expand its fleet and replace the existing F59PH locomotives which had been in service for almost 20 years.

Another ten MP40PH-3C locomotives were purchased later and were delivered in 2013 and 2014 when GO Transit found that additional equipment was required to expand rail service.

It includes two progressive maintenance bays, repair shops for 11 coaches and 12 locomotives, two washing stations and storage tracks for 13 trains.

[59] The facility was constructed to handle service expansions, which include the GO Transit Regional Express Rail program.

[60] Metrolinx is planning a new storage facility along the Richmond Hill GO Line south of Oriole GO Station near York Mills Road.

In December 2018, GO Transit banned CSA Gordon "Gord" Plumridge from singing Christmas carols over the PA system on the train after a complaint from a passenger.

"[71] She stated that a compromise was made between Plumridge and Bombardier, the company who was contracted to provide services to GO Transit.