From 1895, Mr. Henry Gannon and Mr. J.H. Dunkerley were in business in India. They joined together in 1918 to form GANNON DUNKERLEY & CO. In 1924, it was incorporated as a Private Limited Company and the change in management from the previous one to the present one took place in 1946. In 1948, it was converted into a Public Limited Company.

Originally, the Company's activities were mainly in trading. Gannons diversified into Civil Engineering in the early thirties. Several bridges, roads and aqueducts including in-house design for some of them were constructed during this period. Several airfields were also constructed during the Second World War. Gannons were one of the earliest to adopt pre-stressed RCC construction in the early fifties.