Keppel Gate is situated between the 33rd Milestone and 34th Milestone road markers on the Snaefell Mountain Course. The word Keppel is from the Scandinavian for Kappafjall (The champion or hero's mountain). This is probably the Scandinavian name for the nearby Slieau Meayll or Slieau Ree mountains. Keppel Gate was part of the Highland Course and Four Inch Course used for the Gordon Bennett Trial and Tourist Trophy automobile car races between 1904 and 1911. Also, Keppel Gate is part of the Mountain Course used since 1911 for the Isle of Man TT and Manx Grand Prix Races.
The A18 Mountain Road was developed in the mid-19th century from a number of pre-existing roads and paths. This included the building of a number of sheep-gates including the East Mountain Gate, the Beinn-y-Phott sheep-gate and Keppel Gate. The section of road from Keppel Gate to Park Llewelyn is a product of the Disaforesting Commission of 1860. Contemporary photographs of the Isle of Man TT races in the 1920s and 1930's show a sheep-gates at nearby Kate's Cottage and also at Keppel Gate. In the recent building of a TT Marshals' shelter at Keppel Gate, the original stone gatepost from Keppel Gate was incorporated into its design.
The Keppel Gate section of A18 Mountain Road was subject to road re-surfacing work during the winter of 2006–2007 by the Isle of Man Department of Transport.