The advancements Andrew Carnegie made in the steel industry are considered to be his greatest achievement ever. Though Carnegie made many other contributions to society, the steel industry would not be where it is today if it weren't for Carnegie. America wouldn't be where it is today either. What Carnegie did was make steel cheaper and more accessible, where as before it had been very expensive and hard to produce.
"In the early 1870s, Carnegie co-founded his first steel company, near Pittsburgh. Over the next few decades, he created a steel empire, maximizing profits and minimizing inefficiencies through ownership of factories, raw materials and transportation infrastructure involved in steel-making. In 1892, his primary holdings were consolidated to form Carnegie Steel Company."
In 1901, Carnegie sold Carnegie Steel Company to J.P. Morgan for a total of around $480 million. Morgan soon merged Carnegie Steel Company with some other steel companies, making US Steel. Despite a violent labor strike at one of Carnegie's factories, he was and still is considered one of the main figures of the second industrial revolution.