The purchase of a fine property named "Walton", midway on the slope between Cavehill and  Belfast Lough by the Irish Dominican Sisters in August 1930, arose from their reading of the signs of the times. Belfast had developed rapidly as a commercial city in the 1920s and the need for secretarial training for young women was seen by the Sisters as an apostolic challenge to provide such in a religious and cultural atmosphere. In addition, the Sisters saw the need for a Preparatory School which paved the way for the opening of the present Grammar School in 1930. All three schools flourished until the outbreak of war when the Blitz and evacuation seriously affected north Belfast.
Numbers plummeted, at one stage to as low as ten, but the return to peace followed by the 1947 Education  Act meant unprecedented numbers for Fortwilliam since free secondary education was now available for all .

Each decade of the second half of the 20th Century was marked by development and growth both in curriculum, provision of buildings and numbers, the latter rising to 1020 in the 1990s. Over the years, the Sisters purchased five adjoining properties and lands on which they built yet more accommodation and now, poised at the beginning of the 21stCentury, a multi-million pound "state of the art" building to enable the Dominican Sisters to continue their educational aim into the third millennium - the pursuit of Truth in all its forms, intellectual,spiritual and moral.