Motor racing began on the Isle of Man in 1904 with the Gordon Bennett Trial and originally was restricted to touring automobiles.

[5] The Highways (Light Locomotives) Act 1904 passed by Tynwald gave permission to use local roads for the 52.15 mi (83.93 km) Highroads Course for the 1904 Gordon Bennett Trial.

Road widening occurred on the Mountain Course at the Highlander, Laurel Bank, Glen Helen (between the Old Quarry and Brew's Restaurant), and at Brandywell with the removal of the Beinn-y-Phott sheep-gate for the 1935 Isle of Man TT races.

[13] Road Improvements occurred at the 26th Milestone, Greeba Bridge and on the Sulby Straight for the 1938 Isle of Man TT races.

[17] Before the commencement of racing for the 1953 Manx Grand Prix, the cottage at Appledene Corner was demolished between the 6th and 7th Milestone road-side marker on the primary A1 Douglas to Peel road on the Mountain Course.

[19] The approach to the Quarterbridge on the primary A2 Douglas to Peel road was widened and re-profiled and the jumps at the Highlander and adjacent to Ballagarraghyn Cottages were removed for the 1954 Isle of Man TT Races.

[20] Other major course alterations for the 1954 Isle of Man TT Races included road widening at Appledene, Handley's Corner, Barregarrow, Rhencullen, Ballaugh Bridge, Ginger Hall (Sulby), and Kerrowmoar.

[25] During the winter of 1975/76 road-widening and landscaping by the Isle of Man Highway Board occurred at Snugbrough on the primary A2 road at the 2nd Milestone.

This road widening scheme began in February 2008[28] with the removal of trees on the Bemahague Estate which included Government House, the official residence of the Lieutenant Governor, and the creation of a small mini-roundabout.

[29] In August 2009, for the 2009 Manx Grand Prix a section of grass bank is removed from the southern side of Keppel Gate.

The roadway at Hillberry Corner underwent repairs to the carriageway and was resurfaced and re-profiled by the Isle of Man Department of Infrastructure, Highways Division during the spring of 2014.

In April 2015, the Highways Division instigated a programme of landscaping at Keppel Gate including the removal of a small grass bank on the north-eastern side of the corner, road re-profiling and re-surfacing work.

[37] In the 2006 TT practice New Zealander Bruce Anstey achieved the unofficial current top speed record of 206 mph (332 km/h)[38] at the end of Sulby straight on a Suzuki 1000cc machine.

The first race held on 18 June 1936 was won by Charles Holland of the Midland Cycle and Athletics Club in 1 hour, 42 minutes and 57 seconds for one lap of the Mountain Course.

[45] On 6 June 1990 Tony Pond completed the first 100 mph (160 km/h) average-speed lap in 22 minutes, 9.1 seconds driving a Rover 827 Vitesse.

[46] In 2011 Mark Higgins completed a lap in 19 minutes, 56.67 seconds at an average speed over 113 mph (182 km/h) driving a USAC Rally America specification Prodrive prepared 4-door Subaru WRX STI.

In 2014 Mark Higgins broke his own record driving a 2015 model Subaru WRX STI with a lap time of 19 minutes, 15.88 at an average speed of 117.510 mph (189.114 km/h).

[47] On 4 June 2016 Higgins improved on his record with a lap in 17 minutes 49.75 seconds, an average speed of 126.971 mph (204.340 km/h) driving a 2016 model of the same car.

[50] During an early morning practice session for the 1927 TT, Archie Birkin swerved in Kirk Michael village to avoid a fish-van travelling to Peel on the primary A3 road, collided with a wall and was killed.

The corner was then named Birkin's Bend, and afterwards, from 1928, practice sessions for the TT races and Manx Grand Prix were held on closed roads.

In 2013 the Isle of Man Government took the unusual step of naming corners after active competitors, with 23 times TT winner John McGuinness,[54] and Dave Molyneux, the most successful Manxman with 17 wins, being honoured.

[62] From 1928 onwards, practice sessions for the Isle of Man TT Races and Manx Grand Prix were held on closed public roads.

The Thursday afternoon practice session from 13:45–17:00 pm introduced in the late 1950s was discontinued for the Centenary 2007 Isle of Man TT races.

Also during the late 1950s, Appledene Cottage was demolished on safety grounds along with Old Brew's Restaurant near Glen Helen during the early 1960s accompanied by a road widening programme at Greeba Bridge.

There were six fatalities among the competitors at the 1970 Isle of Man TT, including world championship contender Santiago Herrero, making 1970 the deadliest year in the history of the event.

[69][70] Further road safety work during the winter of 1970/1971 road-widening occurred at the Verandah series of bends and also at the Bungalow Bridge by the Isle of Man Highway Board cutting into the hillside.

[81] Following a meeting of the Strategic Motorsport Group organised by the Isle of Man Government, the Clerk of Course announced procedural changes to red flag incidents.