Which of these commodities earned Andrew Carnegie most of his fortune?

I like it when wealthy people think of the greater good

Player #480482, Made is fortune in America but was born and brought up in Scotland.

Mr. Carnegie also built many of the solid brick libraries throughout the United States that are still used. Easy to pick out the brick buildings everywhere.

When Carnegie agreed to $480 million (which was very, very overpriced) he asked Morgan, "If I would have asked for 500 million would you have paid?" Morgan replied, "Be on your way Andrew."

What a Great American ICON.