1

What are bills made of?

Unlike other currencies, dollar bills are not made of paper or plastic. U.S. dollar bills are made from a special fabric blend composed of 75% cotton and 25% linen. This mix makes the bills extremely durable and resistant, and they can be folded about 4000 times before tearing.

2

What bills are valid?

Any U.S. dollar bill that was legally printed is valid, no matter how old, as American currency does not have an expiration date. While some bills might not be accepted by businesses of foreign exchange services due to their condition or if they are a discontinued version of the bill, the bills themselves are still valid, and American banks will accept them, though they might take them out of circulation.

3

American leaders

Five bills have a depiction of an American president. The exceptions are the $10 bill, with Alexander Hamilton on the front, and the $100 bill, with Benjamin Franklin. The $1 bill, depicting George Washington, is extremely symbolic: several elements are repeated 13 times as a nod to the thirteen colonies, and it showcases the Bald Eagle and the Eye of Providence as a sign of God watching over America.

4

A change in size

Did you know that dollar bills used to be so big that they were nicknamed "horse blankets"? Original dollar bills were 7.4 × 3.1 inches. In 1929, the Treasury Department reduced the size of bills to 6.14 × 2.61 inches to reduce production costs and materials. Old bills, though still valid, are worth much more as collector items.

5

Uniformity

Besides their value and design, all dollar bills have the same size (6.14 × 2.61 inches), color, and weight (1 gram) , which sets American currency apart from other countries where bills of different values are differentiated by size, color, or both. Why doesn’t the U.S. implement differences among bills? The cost of adapting vending machines, bank drawers, and ATMs to new bill sizes would cost billions of dollars.

6

Hard to copy

Originally, dollars were not green, but black. As time passed, green ink was favored, as it was cheap and did not fade as much as black. The new color also prevented people from using black-and-white cameras to create counterfeit money. Currently, dollar bills are predominantly green, but newer versions also include extra colors, such as pink, orange, or purple.

7

A $100,000 bill?

Have you ever seen a $500 or 1,000 dollar bill? What about a $100,000? Up until 1945, the U.S. Treasury printed $500, $1,000, $5,000, $10,000, and $100,000 notes , in addition to the values currently in use. These higher-value notes were mainly intended for bank and government use, but were sought by criminals as they made it easier to hide large amounts of money. Even though they were officially discontinued in 1969, these notes are still valid, though rare, and they have a high worth as collector's items.

8

No numbers

Unlike bills, American coins have different sizes and colors related to their value. Originally, gold, silver, and copper were used for coins, but modern coins are made of copper, zinc, or nickel. Besides their size and design, the value of each coin is printed in letters, not in numbers , alongside depictions of American presidents.

9

Liberty for all (the coins)

By law, all American coins must include six specific details : the word ‘Liberty’, the name of our country, the national motto "In God We Trust", the oldest American motto "E Pluribus Unum", the value of the coin, and the year. Each coin also includes a mint mark that shows where it was made: "P" for Philadelphia, "D" for Denver, "S" for San Francisco, and "W" for West Point.

10

A global currency

The American dollar is one of the most powerful currencies in the world, acting as a backbone for international trade and finances. It is estimated that two-thirds of the physical dollars in circulation are outside American territory. Besides the U.S. and its territories, eight sovereign nations have the U.S. dollar as their official currency, with several more accepting it as legal tender.

1

Technology

Image: Shoeib Abolhassani

The U.S. tech sector exceeds $2 trillion in market value and leads the world in software, cloud computing, and semiconductor innovation.

While major hubs like Silicon Valley concentrate much of the activity, the industry has a nationwide footprint—from research centers and investor networks to hardware design and advanced manufacturing. Also, AI investment now represents a substantial share of the sector, which remains overwhelmingly U.S.-driven.

2

Healthcare

Image: Piron Guillaume

Healthcare spending in the U.S. surpassed $4.5 trillion recently, accounting for nearly 20% of GDP. Hospitals, insurers, biotech firms, and pharmaceutical companies together form the largest employment ecosystem in the country.

Moreover, the pharmaceutical segment alone exceeds $600 billion, placing the U.S. at the forefront of global drug development and clinical research.

3

Finance

Image: Nick Chong

Banking, investment, and insurance services generate over $2.5 trillion annually, and Wall Street remains the world’s largest capital market by trading volume.

Believe it or not, U.S. asset managers oversee more than $30 trillion in global funds, a scale unmatched anywhere else. American payment networks and credit systems also form a major part of the infrastructure that supports international commerce.

4

Energy

Image: Documerica

The U.S. is one of the world’s top producers of oil and natural gas, with the energy sector generating hundreds of billions of dollars each year. Texas is the largest state contributor, while New Mexico and North Dakota also rank among the leading producers.

Although renewables now surpass several fossil fuels in total electricity generation—driven largely by wind and solar—the energy sector as a whole remains robust and highly diversified.

5

Manufacturing

Image: Simon Kadula

Manufacturing underpins the growth of countless other industries, and American heavy industry contributes more than $2.3 trillion to GDP, spanning automobiles, machinery, electronics, and advanced materials.

The sector employs over 12 million people and remains a global leader in areas like industrial automation, chemical production, medical devices, and food processing. U.S. factories also rank among the world’s most productive thanks to high-tech equipment, robotics, and supply chains that integrate everything from raw materials to final assembly.

6

Retail

Image: Viktor Bystrov

Feel like going shopping? You’re certainly not alone—the U.S. retail sector generates over $7 trillion annually. Big-box chains, e-commerce giants, and grocery networks together make up one of the nation’s largest employment sectors.

E-commerce alone now exceeds $1 trillion, fueled by major progress in logistics, fulfillment technology, and nationwide delivery networks.

7

Agriculture

Image: Hannah Shedrow

The fertile Midwest and Great Plains are often called the "breadbasket of the world," and it’s no exaggeration—U.S. farms produce more than $500 billion in goods each year.

While corn, soybeans, beef, and dairy dominate overall output, the sector supports a wide array of other crops and livestock. It also drives innovation in precision machinery, fertilizer development, and agricultural technology that shapes global food production.

8

Transportation

Image: Documerica

Transportation is a massive sector—covering airlines, shipping, trucking, and rail—and generates more than $1.4 trillion annually. Trucking alone moves over 70% of domestic freight, while rail remains essential for transporting bulk commodities like grain, coal, and industrial materials.

Air travel supports millions of jobs, with major hubs such as Atlanta and Dallas ranking among the world’s busiest by passenger traffic. Ports like Los Angeles, Long Beach, and Houston handle some of the highest cargo volumes in the Western Hemisphere, while the U.S. highway system remains one of the largest and most heavily used in the world.

9

Construction

Image: C Dustin

In a country where iconic skylines are considered part of the landscape, construction is naturally a major economic force. The sector now exceeds $2 trillion in annual output, driven by persistent housing demand and large-scale commercial development.

Infrastructure also accounts for a significant share of spending, covering everything from bridges and tunnels to highways and transit systems. Residential building cycles strongly influence employment, making construction one of the most sensitive indicators of broader economic health.

10

Aerospace & defense

Image: Hermeus

As one of the world’s leading centers of innovation, the U.S. aerospace sector—often intertwined with the defense industry— contributes more than $400 billion annually, driven by aircraft manufacturing, satellite technology, and advanced defense systems.

Government defense spending, which exceeds $800 billion per year, supports major contractors, sustains global military partnerships, and helps maintain a technological edge over international competitors.

1

Thomas Edison

Image: Call Me Fred

When it comes to inventors, we can't fail to mention the incredible Thomas Alva Edison.

Edison was born on February 11, 1847, in Milan, Ohio, and since he was a child, he showed his interest and talent in mechanics and electricity. At the age of 11, he set up his first laboratory in his parents' home, and by the age of 12, he ran his own business: a newspaper he designed, printed, and sold himself.

Creator of the phonograph (the first device capable of recording and reproducing sounds) and a fundamental part in the development and popularization of inventions such as the electric light bulb and the motion picture camera, Edison patented more than 1000 creations during his lifetime. Impressive!

2

Benjamin Franklin

Image: Dan Mall

Born in Boston, Benjamin Franklin was one of our Founding Fathers, the men whose principles, values, and ideas shaped America. But as if that weren't enough, Franklin was also a renowned scientist, inventor, and polymath.

A pioneer in the field of electricity, he's remembered for his famous kite experiment, which demonstrated the electrical nature of lightning and led to the invention of nothing less than the lightning rod. In addition, he's also credited with iconic inventions such as the first efficient wood-burning stove (later known as "the Franklin Stove"), the bifocal glasses, and the glass armonica.

3

Samuel Morse

Image: The New York Public Library

Unlike other scientists and inventors on this list, Samuel Morse began his journey in a completely different field: art.

Morse studied at Yale, where he completed his studies in 1810. He then embarked on a trip to Europe to continue his artistic education, but this trip awakened another peculiar interest in him. Frustrated by the communication methods of his time, Morse focused his creativity on finding ways to transmit information over long distances using electrical signals. Thus, the revolutionary telegraph was born, along with its way of communication, the Morse code.

4

The Wright Brothers

Image: Simon Fitall

The Wright Brothers were the famous siblings who, in the 20th century, achieved a goal long sought by humanity: flight.

Wilbur and Orville Wright are credited with inventing, building, and flying the world's first successful airplane. As you probably know, on December 17, 1903, they made the first sustained flight in history using the Wright Flyer, their iconic invention.

On that December morning, the brothers flipped a coin, letting fate decide who would be the first to test the aircraft. Although Wilbur won, that first attempt failed. So it was Orville who flew for 12 seconds, traveling 120 feet over Kitty Hawk, North Carolina.

5

George Washington Carver

Image: Tom Hermans

George Washington Carver was born in the 1860s in Diamond, Missouri. In the 1890s, his intelligence and hard work enabled him to enter Iowa State College (now Iowa State University), where he earned a master's degree in agricultural sciences. In 1896, he became the head of the agriculture department at Tuskegee Institute in Alabama, where his career as a professor and a researcher took off.

Thanks to his investigations and tests, George Washington Carver made major contributions to agriculture, including his innovative techniques for crop rotation . In addition, he developed many and varied peanut products, such as oil, flour, soap, and ink, helping to make this crop one of the key products of the country's economy.

6

Carl Sagan

Image: Vaibhaw Kumar

The stars and the mysteries of the universe captivated the famous Carl Sagan from an early age. Born in Brooklyn, New York, in 1934, Sagan studied at the University of Chicago, where he earned degrees in physics, astronomy, and astrophysics, eventually working and collaborating with NASA.

His contributions to the field of astronomy earned him a position in projects such as the Mariner, Viking, Voyager, and Galileo missions, thanks to which we have learned a lot about Venus, Mars, and Jupiter. The famous high temperatures of Venus, for example, were confirmed thanks to his work.

Additionally, his book and series Cosmos attracted the public's interest in astronomy, inspiring many others to follow in his footsteps.

7

Grace Hopper

Image: Museums Victoria

While computer programming may seem like a modern issue, the pioneers of this field were already working as early as the 1940s.

Grace Hopper graduated in mathematics and physics in 1928 and obtained a master's degree and a Ph.D in mathematics from Yale University in 1934. Famous as a pioneer in the world of programming, Hopper's work began during World War II when she joined the US Naval Reserve. There, she worked on the earliest electromechanical computers and developed extensive and complex manuals to operate them.

Her greatest contribution came from her work with mathematical codes, which she translated and adapted into innovative machine-readable language. That innovation led to the creation of the first high-level programming languages.

8

Jonas Salk

Image: Олег Мороз

Jonas Salk is none other than the mind behind a medical milestone: the polio vaccine.

In the 1940s, Salk was beginning his career in medical research. While working at the University of Michigan, his work was crucial in developing the first successful influenza vaccine for the military during WWII. This event marked his later study of the poliovirus.

Polio was devastating during the first decades of the 20th century, but that changed dramatically thanks to Salk's work. The scientist led a team that succeeded in developing the first safe and effective injectable inactivated poliovirus vaccine (IPV) in 1955, and the rest is history.

9

Barbara McClintock

Image: digitale.de

Although her name may not be as instantly recognizable as some others on this list, her work definitely is. Barbara McClintock has undoubtedly made one of the most significant contributions to medicine and genetics.

In the 1940s and 1950s, she worked with chromosomes, investigating their role in inheritance, which led to discoveries that forever changed our understanding of genes.

Before her, genes were believed to be fixed and immutable. But McClintock came to change that idea with her most famous contribution: the discovery of transposable elements, aka "jumping genes." She demonstrated that jumping genes are present in multiple organisms, including humans, and play an essential role in genetic evolution.

10

Alexander Graham Bell

Image: Misho Tektumanidze

Alexander Graham Bell became interested in sound and communication at a young age, something that led to his greatest and most remembered contribution: the telephone.

Although born in 1847 in Edinburgh, Scotland, Alexander Graham Bell settled in the United States in 1871 and became an American citizen years later. It was here that he developed most of his experiments and research.

After years of experimenting with methods to transmit sound through electrical currents, Bell finally spoke into his invention on March 10, 1876, saying to his assistant, "Mr. Watson, come here. I want to see you." That was the first successful telephone call in history.