Eglinton Iron Company was incorporated c.1845 by William Baird and Co to manage and operate their new iron works at Eglinton, and later the extensive mineral leases at ironworks at Blair, Muirkirk, Lugar, and Portland.
The Scottish Iron and Steel Company was incorporated as a limited company in 1912, by the amalgamation of thirteen firms: Archibald Baird and Son Ltd; Downs and Jardine; Thomas Ellis Ltd; Glencairn Iron and Steel Co Ltd; C. F. MacLaren and Co; Hugh Martin and Sons; A. and T. Miller; John Spencer (Coatbridge) Ltd; William Tudhope and Son Ltd; Victoria Iron and Steel Co Ltd; Waverly Iron and Steel Co Ltd; Wylie and Co; Woodside Steel and Iron Co Ltd.
The specialities of the company included: iron and steel bars, angles, tees, hoops, and strips. The Northburn Iron and Steel Works was completed in 1920 and housed the first electrically-driven reversing mill to be erected in Scotland.
In 1938, the Scottish Iron and Steel Company Ltd was merged with William Baird and Company Ltd to form Bairds and Scottish Steel Ltd, pig iron and steel manufacturers.