In 1911, Harry started his own garage and car sales business in Belfast - the May Street Motor Company acquiring the agency for Vauxhall and Austin. He had two outstanding engineers working for him at this time who were to remain with him, playing a major part in his later success.

The firm prospered and took on agencies for Vauxhall and Ford cars. He started to sell Overtime tractors imported from America in 1914. These early tractors were very costly, heavy, difficult to handle and potentially dangerous. To Harry their greatest drawback was that most implements were simply trailed behind the tractor, working agaianst rather than with the tractor, seperate rather than integrated as a single unit.


At the start of the First World War, with the German stranglehold tightening on ships bringing foodstuffs from America, Harry was asked by the Government to tour Ireland and train farmers on how to use their tractors to their full potential. Horses were in short supply as the army had requisitioned most of them to tow the big guns in France, so tractors were now crucial in crop tillage. But Harry discovered that tractors of the period were seriously flawed. Nor, despite his efforts, could he find ways to improve them. Finding none suitable for modification, he designed a model of his own onto which he built the revolutionary three-point linkage with hydraulically operated depth control. This took many years to perfect, but, when completed, finally provided a solution to the perennial problem of the tractor tipping backwards when the plough encountered an obstacle, sometimes with fatal consequences for the driver.


From the start Harry's dream was to try to unify and simplify his products for a global market. The First World War created a national crisis, and there was a need to increase home food production to prevent starvation. Speaking at the International Food Conference at Bethesda, Maryland USA on the June 5th 1943 stated, "My whole economic philosophy and all my efforts are guided by the knowledge that the best way to improve the total economy will be through cutting the costs of production of agricultural products, which control the cost of living." Harry literally wanted to erase poverty worldwide.


The success of 'Harry Ferguson Limited' had enabled the firm to obtain several valuable motor agencies and among them was the Vauxhall agency. Vauxhall was considered one of the faster and more sporty marques at the time and these attributes were right up Harry’s street, renewing his interests in competitive motoring. Soon he had a number of successes while driving Vauxhalls in local Irish Trials and the Vauxhall company took notice, offering him a 3 litre works car to compete in the 1912 French Grand Prix.