The Douglas Engineering Company was formed in Bristol by brothers William and Edwin in 1882, at first as a blacksmiths shop but soon expanding to become an ironfounders. With the turn of the century and the advent of the motor vehicle, the company quickly became involved in the development of engines.
The first Douglas motorcycle appeared in 1907, although the Douglas company had supplied engine castings to the Bristol engineer Joseph Barter for his earlier Fairy motorcycle which would become the basis of the Douglas design. There followed a long line of horizontally opposed twin cylinder machines of 2.3/4 HP, right through to the late 1920s. The 1914-18 War saw production in large quantities for the war effort and also the start of the 3.1/2 HP models, followed closely by the 4 HP machines. During the 1920s many others followed such as the 350cc EW, 500cc and 600cc models and speedway machines. In the 1930s a wide range of machines was produced including the S6/T6, the Endeavour (the first transverse twin) and finally the pre-war Aero models. After the Second World War, during which Douglas manufactured horizontally opposed stationary engines, they restarted motorcycle production with the 350cc Mk I or T35, followed by the Mk 3 and Mk 4 models, both with sports variants.
The start of the 1950s saw the Mk 5 variant with the Competition and Plus series models. The final model, the Dragonfly, still a horizontally opposed twin, was announced in 1954 with production finally ending in 1957 after an overall marque life span of just 50 years.