Iron+and+Steel

“//the old cast iron buildings died out. I'm not really sure whether the new skyscrapers killed them, or the new esthetics//”

It was //not only// the fact that now they could build taller buildings with steel girders, or that there were new esthetics; I think that cast iron became obsolete when steel was introduced. Steel was lighter and it could overcome corrosion, and in general it was stronger and more long lasting than cast iron. Plus, cast iron buildings couldn't resist a fire, unlike steel.