Tobacco merchant. The son of a maltman, George Buchanan (1686 - 1773) and nephew of another Andrew Buchanan (1690 - 1759), who had grown wealthy as a Tobacco Lord. He had other uncles in the same trade and Buchanan became head of two merchant companies; Buchanan, Hastie & Co. and Andrew Buchanan & Co. However, in 1777, both businesses failed when their tobacco estates were lost following the American Revolution.
In 1763, Buchanan had been able to buy 1.6 ha (4 acres) of land in Central Glasgow, on which he built a house. After the crash he dismantled much of the house in order to feu the land for development. He died before his plans could be implemented but his trustees continued the project to provide for his family, naming the development Buchanan Street in his memory.
