This thesis describes the origins of the Scottish architectural iron founding industry. It also investigates the underpinning reasons for the proliferation of the Scottish industry in terms of the technological context and the complex inter–relationships of the key figures and firms involved. The founding of Carron in 1759, combined with the discovery of blackband ironstone and the means to smelt it, prompted the rapid growth of the iron founding industry at the start of the 19th century. The influence of Carron in propagating a broader industry and the evolution of the early architectural specialists are discussed. Accounts are given of the key Scottish firms and projects and structures are considered in detail. The Saracen Foundry of Walter Macfarlane and Co is identified as a firm of international importance. The comparative outputs of the key firms in relation to known structures are considered as well as the decline of the industry towards the end of the 20th century. Significant works of innovation are identified which have not previously been appreciated in early iron façade construction at Perth Waterworks, and possibly the earliest iron glasshouse at Fairfield House in Dalkeith.