When you google Andrew Carnegie you'll get biographies about how he was the most influential philanthropist in the world, and his story is a true "rags to riches" tale.
Carnegie, a Scottish immigrant, got a promotion at the Pittsburgh Railroad Company when he was 24 for figuring out a way to keep the telegraph office open 24/7. He made investments in the growing railroad industry (notably the iron bridge company Keystone Bridge Company and telegraph companies), using the insider-knowledge and contacts to his advantage. At age 28 he's rich enough to buy a 'substitute' when he's drafted for the Civil War. The substitute fee is $300, $6,228 in 2021 dollars. At age 30 he quits the PRC and starts buying up as much steel companies as he can. The railroad business is booming, the skyscraper business is booming...Carnegie had the biggest head start and he never looked back.
27 years later, in 1892, he consolidates all the companies he's acquired into Carnegie Steel Company. He always said he was a friend to workers, he himself was a worker since he was 12. But his first order of business after consolidating was to break a union at one of his plants in Homestead. He actually was on vacation in Scotland when he oversaw what would be one of the bloodiest labor disputes in American history.
The steel workers had a strong union (Amalgamated Association of Iron and Steel Workers, eventually today's United Steelworkers). Before it became Carnegie Steel, they organized the plant run by Pittsburgh Bessemer Steel Works in 1881 to fight the practice of yellow-dog contracts--an agreement management would make workers sign before hiring them that says they can not join a union. It was a 3 month long fight with violence and strikebreakers but the union won.
In 1889, negotiations for a new 3-year contract stalled. The union asked for a wage increase proportional to the increase in the price of steel, Carnegie and Frick countered with a 22% wage decrease. The nearby steel mill Edgar Thomson and Duquesne had newer, more efficient equipment and Carnegie and Frick ordered that production times were sped up to keep up, but the union refused. Carnegie and Frick locked out the workers in 1892, so the workers went on strike. Carnegie and Frick sent in 300 armed Pinkertons by boat at 4am to break the strike. But 10,000 armed workers were waiting for them. 7 Pinkertons and 9 workers would die in the skirmishes. During the 12 hours of battle, a union leader asked the sherriff's office to meet with Frick to restore the peace. Frick refused, knowing that the governor would eventually send in state militias if the situation remained chaotic. The Pinkertons surrendered. Carnegie and Frick called the governor and 8,500 National Guard troops were sent to Homestead. Carnegie and Frick were now able to open the plant back up with 1,700 scab workers under the protection of the 8,500 troops.
Andrew Carnegie was not a friend to workers.
In 1901, JP Morgan buys Carnegie Steel for $480 million ($14.7 billion in 2021 dollars) and consolidates it and a group of other steel companies to form US Steel.