Montreal Biosphere / Buckminster Fuller. Image © Flickr user abdallahh
The advent of steel in architecture at the beginning of the 20th century is considered as one of the most innovative construction developments in history, allowing architects to create structures with heights, flexibility, and freedom never seen before. Henry Bessemer invented the most successful steel-making process in 1855, but it was not until 1890 that the process was refined enough for construction. The first steel constructions on both sides of the Atlantic, the Rand McNally Building in Chicago and Forth Bridge in Edinburgh, were record-breaking structures of their time.