A Richmond Hill commuter train service had been announced in 1969 by the provincial government, but its implementation was cancelled in 1970 in favour of bus commuter service.
After the Lakeshore East, Lakeshore West, and Georgetown lines, the Richmond Hill line was the fourth in the GO network to open. Following a promotional opening on Saturday April 29, 1978, regular service began on Monday May 1. Unique amongst GO rail corridors, the initial lineup of four stations has not changed since opening day.
As part of the GO 2020 strategy, the corridor will be upgraded and extended to Aurora Road in Stouffville. Phase I of the project, for which construction will begin in the fall of 2011 and be completed in the fall of 2013, will establish the Gormley GO Station where the line intersects Stouffville Road, create a train layover facility at Bethesda Road, and grade the corridor for the extension. Phase II, which will begin after completion of Phase I, will consist of the construction of Bloomington GO Station and grading of the route.
On April 16, 2015, the Ontario government is working with Metrolinx to have more train service along the Richmond Hill line, known as GO Regional Express Rail over the next decade. During peak hours, trains would run in peak direction every 15-30 minutes along this line.