AP® United States History · Unit 6 · Topic 6.5
Steel, Electricity, and the Telephone
Cheap Bessemer steel and citywide electrical grids gave builders a strong light frame and a way to move people up it, so cities started building vertically instead of just outward.
Before the Bessemer process, steel was made in small, slow, expensive batches, fine for tools but not for building cities. The Bessemer process blows air through molten iron, and the oxygen reacts with carbon and other impurities, burning them off in minutes instead of days. The result is steel, strong and light compared to iron, produced fast and cheap, in volumes large enough to frame buildings and lay thousands of miles of track.
Electricity spread the same way steel did: from one point outward at massive scale. A generating station produces current, then wires carry it out to homes, factories, and streetlights across a district. Edison's direct current loses power quickly over distance, so it only worked near the plant. Alternating current, pushed by Westinghouse and Tesla, can be stepped up to high voltage for efficient long-distance transmission, then stepped back down for safe use. That is the real reason AC won: not a better inventor, but a current built for distance, which is what any citywide or regional grid actually needs.
Put steel and electricity together and the skyscraper becomes possible. A steel frame carries the building's weight instead of thick masonry walls, so builders can go up far higher using far less material. But height is useless if people have to climb it, so the electric elevator, running on the same grids being built out everywhere, makes those upper floors reachable in seconds. Steel gives buildings their height, electricity gives them their reach, and together they turn city skylines from low and wide into tall and dense.
Key terms
- Bessemer process
- A method of making steel by blowing air through molten iron to burn off impurities quickly and cheaply.
- direct current (DC)
- Electric current that flows in one direction and loses power quickly over long distances, Edison's preferred system.
- alternating current (AC)
- Electric current that reverses direction and can be transmitted efficiently over long distances, the basis for modern power grids.
- electrical grid
- A network of wires carrying electricity from a central generating station out to many homes and businesses.
- steel frame construction
- A building method where a steel skeleton bears the structure's weight, allowing much greater height than load-bearing walls.
Watch it explained
- How it worksWalk me through the Bessemer process blowing air through molten iron to make steel in minutes.
- How it worksHow does an electrical grid get built out from one generating station to a whole district?
- Common mistakeWhy isn't Edison's advantage in the electricity fight the better technology?
- Ties togetherHow do the elevator and the steel frame together make the first skyscrapers possible?
Check yourself
End of topic.