Historical information
It took eight years, five major contractors and the relentless labour of 432 construction workers to build Tower Bridge.
Two massive piers were sunk into the river bed to support the construction and over 11,000 tons of steel provided the framework for the Towers and Walkways. This framework was clad in Cornish granite and Portland stone to protect the underlying steelwork and to give the Bridge a more pleasing appearance.(http://www.towerbridge.org.uk/bridge-history/)
