Steel is an alloy, or a mixture. Steel makers combine iron and carbon. A strong, inexpensive material forms.

That alloy is big business. But it’s also big history. People have been making steel for thousands of years.

If you needed steel during the Middle Ages, you’d visit the blacksmith. These artisans often used steel to create swords, armor, and tools. But steel got really big during the Industrial Revolution in the 1800s. People learned to make bigger, more efficient furnaces for smelting ore. Instead of crafting enough for just one sword at a time, they could make huge amounts of steel at once.

In 1901, some of America’s most famous businessmen started U.S. Steel. You might see the names of some of these businessmen on banks today. For example, J.P. Morgan was a banker. He helped bring many large steel companies together into one. This included the Carnegie Steel Company, owned by Andrew Carnegie, one of the richest men in the world. The new company operated out of Pittsburgh, Pennsylvania. That town became known as “the Steel City.” (Ever heard of the football team the Pittsburgh Steelers? They got their name from their steel-rich hometown.)

U.S. Steel grew steel-strong. It supplied metal for World War I. The Great Depression hit in the 1930s. Many companies collapsed at this time. People grew terribly poor, and many needed work. But U.S. Steel didn’t die. It kept going. Afterward, it created more metal for World War II, when soldiers needed much steel for helmets, weapons, ammunition, tanks, and ships.

And steel didn’t stop there. The United Nations Building in New York City? That’s U.S. Steel. The San Francisco-Oakland Bay Bridge? Same. Pablo Picasso’s unnamed Chicago sculpture? You guessed it: steel again.