It took three great ideas and an entrepreneurial genius to redefine cities and the way people live and work in them.

Steel magnate Andrew Carnegie began as a railroad clerk, quickly worked his way to the top and became rich through insider trading and monopolistic businesses that would be illegal today, although he was a great philanthropist who believed that it was shameful to die a rich man.

He foresaw that longer and heavier trains would require sturdier bridges built from iron rather than wood. After founding an iron company and acquiring an interest in what would become his Keystone Bridge Co., he revolutionized the iron industry by centralizing all phases from ore to product under one operation.

By increasing factory output and combining iron production with the bridge-building company, he drastically cut the time and labor required to move material.

After building his first blast furnace, he discovered that no one knew much about what went on inside the furnace, so he hired engineers to increase its efficiency by studying the reduction chemistry of the furnace.

His chemists devised a way to improve the efficiency of the reaction in the furnace according to quality of the iron ore, and they figured out a way to increase the output even more by removing the slag from the furnace faster.

One brilliant innovation was using a cost accounting system (basically a spreadsheet) to analyze the plant figures to make an important discovery that doubled the output of the furnace as it also reduced the long-term operating costs.

He returned from a trip to England in 1872 where the Bessemer process was being implemented, which could make hard steel from soft iron by burning off the impurities with a blast of oxygen.

Carnegie saw that the American rail system would have to convert to steel rails because they were much stronger and more durable than iron rails by a factor of 15-to-20.

It just happened that in 1868 iron ore from the Upper Peninsula of Michigan was determined to have the low phosphorus content that the Bessemer process required, and by 1871 transportation lines could supply large amounts of ore to the steel mills in and around Pittsburgh.

With the railroad growing westward and the ability to transport cheap iron ore, Carnegie decided that he had to build a brand-new massive plant devoted solely to making Bessemer steel railroad rails.

Between 1870 and 1880, 40,000 miles of railroad track was laid in the United States, mostly with Bessemer steel rails.

In 1889 the Tacoma Building in New York City became the first structure ever built where a cage of Bessemer steel beams rather than the outside walls carried the weight of the building. Some call it the first skyscraper.

Steel became the miracle metal and transformed 20th-century architecture and engineering as steel-framed buildings soared hundreds of feet to scrape the sky.

Two additional inventions were necessary to make the modern skyscraper possible, the elevator and the telephone, both of which just happened to be developed around the same time.

Richard Brill is a professor of science at Honolulu Community College. E-mail questions and comments to rickb@hcc.hawaii.edu.