McCullagh started his career as an apprentice at the age of 14 in the drapery trade. He then became the director of several businesses in Belfast, including Maguire and Patterson, a dry goods firm (Vespa matches), and the Classic Cinema at Castle Place, as well as owning McCullagh and Co., a silk mercers, milliners and fancy drapery store taken over by Styles and Mantles in 1927.
McCullagh was not the pioneer of the ‘Two Minutes Silence’, as Newtownabbey author Bob Armstrong claimed in his publication ‘Through The Ages To Newtownabbey.’ According to the Belfast Telegraph at the time Sir Crawford called for a ‘Five Minutes Silence’ on 11 July 1916, following receiving news of the death of thousands of soldiers from the 36th (Ulster) Division at the Somme. However, significantly, he was the first recorded person to publicly call for a period of silence for fallen soldiers.
McCullagh was knighted on 19 May 1915, and created a baronet on 1 July 1935