He was the son of the Reverend James Johnston, of Springburn's United Presbyterian Church.
George spent the early part of his career in locomotive engineering before designing and constructing Scotland's first automobile, the Mo-Car, which led to the formation of the Arrol-Johnston Car Company Ltd. George Johnston worked as a locomotive engineer for Neilson, Reid and Company's Hyde Park Works of Springburn, Glasgow.
[1] In 1894 Johnston was commissioned by Glasgow Corporation to build an experimental steam tram-car to replace the horse trams.
Johnston's attention was then turned to a detailed examination of continental makes of motor car.
In the autumn of 1895 Johnston was joined by his cousin Norman Osborne Fulton and T. Blackwood Murray, former Works Manager with Mavor and Coulson, makers of mining machinery in Bridgeton.