Built the largest steel operation in the United States
Understood his costs in more detail than anyone else in the industry, and used it to price competitors out.
Photograph: Theodore C. Marceau · Public domain · Wikimedia Commons
Carnegie emigrated from Dunfermline to Pennsylvania as a child and worked his way up through the telegraph office and the railways before moving into iron and then steel. He adopted the Bessemer process early and built at scale when others hesitated.
His real edge was accounting. Coming from the railways, he brought cost accounting into steelmaking — knowing what each department cost per ton, comparing plants against each other, and pushing relentlessly on the numbers. Competitors often did not know their own costs to the same precision.
He bought the iron ore, the coke, the ships and the railways feeding the mills, so margins his suppliers had been taking became his. He also invested hard in downturns, when capacity was cheap, and came out of each recession with a stronger position.
Knowing his costs to the ton let him cut prices in a slump and still make money, while rivals who were guessing had to guess whether they could follow.
Carnegie could discount because he knew exactly where the floor was. Most owners have a rough idea of overall profitability and no idea of the cost of one job, one product or one customer — which makes every pricing decision a nervous guess. Work out the cost of one unit of the thing you sell, honestly, including the time nobody bills.
Integrating backwards captures margin and secures supply, and it makes sense once you are a big enough buyer that the supplier's profit on you exceeds the cost of doing it yourself. Below that line it is a distraction, and plenty of small firms have bought a supplier and inherited a business they did not understand.
Buying capacity in a downturn is how he compounded position, and it requires the balance sheet to survive the downturn first. That is the order: liquidity, then opportunism. Doing it the other way round is how firms disappear.
The cost discipline was applied to wages and conditions too. The 1892 Homestead strike ended in lethal violence between striking workers and hired Pinkerton agents, and it permanently marked his reputation. Henry Clay Frick ran the plant and directed the confrontation; Carnegie distanced himself from it afterwards, which persuaded few people.
He later gave away the great majority of his fortune, funding libraries and institutions on a scale that still shapes public life. Both facts are true at once, and a profile that reports only the philanthropy is not an honest one.