By 1911 Pittsburgh was the nation's 8th-largest city, accounting for between a third and a half of national steel output. Andrew Carnegie, from Dunfermline, founded the Carnegie Steel Corporation which eventually became US Steel (still the 15th largest steel producer in the world, as of 2014).

And, like Iowa with it's corn in everything you eat and drink, Pittsburghers (as they are known) used a lot of steel to make a lot of bridges, like this:

You can see more steel along Pittsburgh's Allegheny river here in the opening scene from the 2012 Jack Reacher movie:

 One notable person from Pittsburgh is Gene Kelly. Even he couldn't avoid steel: