1

Harriet Tubman secretly worked as a Union spy

Most Americans know Harriet Tubman for her leadership of the Underground Railroad, but during the Civil War, she also became a Union scout and spy in South Carolina. Working with Colonel James Montgomery, Tubman gathered intelligence from enslaved people living behind Confederate lines near the Combahee River .

In June 1863, Tubman helped lead the Combahee River Raid, guiding Union gunboats through Confederate waters filled with hidden mines. The operation freed more than 700 enslaved people and made Tubman the first woman known to lead a major U.S. military mission.

2

Julia Child worked for the U.S. intelligence agency

Before becoming television’s most famous chef, Julia Child joined the Office of Strategic Services, or OSS, in 1942 during World War II. The OSS later evolved into the CIA. Too tall to enlist in the Women’s Army Corps, Child instead classified files and overseas communications in Asia.

One of her strangest assignments involved helping researchers develop shark repellent for Navy explosives and emergency rescue kits . The repellent used copper acetate and black dye to create an odor similar to a dead shark.

3

Benjamin Franklin conducted unofficial spy work in Europe

Benjamin Franklin was more than a scientist and Founding Father. During the American Revolution, he quietly acted as an intelligence organizer while serving as ambassador to France beginning in 1776 . Franklin cultivated secret alliances, intercepted information, and used coded correspondence to support the colonies’ fight against Britain.

Operating from Paris, Franklin built relationships with French officials and helped persuade France to support the American cause with money, troops, and naval power. Historians consider his diplomatic intelligence efforts essential to the American victory at Yorktown in 1781 and eventual independence.

4

Louisa May Alcott published thrillers under another name

Louisa May Alcott became a literary icon after publishing Little Women in 1868, but few readers knew that she had already written sensational thrillers under the pen name "A.M. Barnard." These stories featured revenge, hidden identities, forbidden romance, and dramatic crime plots that shocked Victorian audiences.

Alcott used a pseudonym because publishers often expected women writers to produce respectable domestic fiction. Many of her darker stories remained forgotten until scholars rediscovered them in the 1940s. Today, titles like Behind a Mask reveal a far more rebellious side of the beloved author.

5

Maya Angelou worked as San Francisco’s first black female cable car conductor

Long before becoming a celebrated poet and author, Maya Angelou made history in San Francisco during the 1940s. At only 16 years old, she applied repeatedly for a conductor job on the city’s cable cars after seeing an advertisement that excluded Black applicants .

Angelou refused to give up despite repeated rejection. She eventually became San Francisco’s first Black female cable car conductor in 1944. Years later, she described proudly wearing the blue uniform while working long shifts across the city before launching her writing and civil rights careers.

6

Dr. Seuss created classified wartime propaganda films

Before writing Green Eggs and Ham and The Cat in the Hat , Theodor Geisel, better known as Dr. Seuss, worked on wartime propaganda during World War II. Between 1943 and 1945, he joined director Frank Capra’s Signal Corps unit to produce military training films for American soldiers .

Geisel also drew political cartoons supporting the Allied war effort and criticizing fascism. Some of his films were classified during the war because they contained military training material. His animated work helped explain battlefield strategy and morale issues to thousands of U.S. troops overseas.

7

Babe Ruth once played an entire game with a fever over 102 degrees

In 1925, Babe Ruth became seriously ill during spring training and collapsed while traveling by train . Newspapers nicknamed the incident "the bellyache heard around the world." Reports from the time described Ruth suffering from a fever above 102 degrees while still insisting on returning to baseball activities.

Despite his condition, Ruth’s determination became part of baseball legend. The illness hurt his performance during the 1925 season, when the New York Yankees finished seventh in the American League. Even so, Ruth rebounded quickly and helped lead the Yankees to championships in later years.

8

Harry Houdini worked with police departments

Harry Houdini’s famous escape acts fascinated police departments across America and Europe in the early 1900s. Officers regularly challenged him to escape from handcuffs, prison wagons, and locked jail cells. Houdini often invited local police to inspect restraints before his performances began.

Beyond entertainment, Houdini also worked closely with law enforcement to expose fraudulent mediums and fake spiritualists during the 1920s . Using his knowledge of locks, hidden compartments, and deception, he publicly demonstrated how many supposed supernatural tricks were actually carefully staged illusions.

9

Frank Lloyd Wright hid a private apartment inside one of his buildings

Architect Frank Lloyd Wright secretly maintained a private apartment inside his famous Oak Park Studio near Chicago, Illinois. Built in the 1890s, the studio served as both his workplace and personal retreat while he designed many of his early Prairie-style homes across the Midwest.

The hidden living quarters allowed Wright to work late into the night and host select guests away from public attention. The building itself became one of the most important centers of American architecture, producing groundbreaking residential designs that influenced modern architecture around the world.

10

Muhammad Ali quietly funded humanitarian causes for years

Muhammad Ali’s boxing fame often overshadowed his enormous charitable work. For decades, Ali quietly donated money to hospitals, food programs, children’s charities, and international humanitarian efforts . Friends and family later revealed that many of his contributions were intentionally kept private.

In 1990, Ali traveled to Iraq during tensions leading up to the Gulf War and helped secure the release of 15 American hostages. He also supported global relief organizations and Parkinson’s disease research after his own diagnosis. In 2005, President George W. Bush awarded Ali the Presidential Medal of Freedom.

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

There's an unexplained billion-year gap

Look closely at the canyon walls, and you'll notice something strange: a clean, sharp line where ancient rock simply stops, and a much younger layer begins directly above it.

This geological puzzle is called the "Great Unconformity," and it represents over a billion years of rock layers that are simply absent , as though that stretch of time never happened. In some spots, rock dated 1.8 billion years old sits directly beneath rock that is only 520 million years old. Where did the missing billion years go?

The leading theory involves the violent breakup of an ancient supercontinent, but scientists are still piecing it together.

2

During the Cold War, it hid a nuclear fallout shelter

During the Cuban Missile Crisis in 1962, the U.S. government converted part of the Grand Canyon Caverns into a fallout shelter. This dry cave system, more than 200 feet underground, was stocked with enough food and water to sustain 2,000 people. Naturally, it was never occupied, and the supplies were never used.

The caverns have since been transformed into a tourist attraction, with organized tours winding through the same underground chambers that were once intended as a refuge from nuclear war. You can even book a night's stay there.

3

The Federal Aviation Administration was founded after a crash over the canyon

In 1956, two commercial passenger planes collided in midair over the eastern Grand Canyon, killing all 128 people on board both crafts. Rescue teams struggled to reach the wreckage deep inside the canyon, and the extreme heat of the crash had caused the planes' aluminum to fuse with the bedrock. There were no survivors.

The disaster exposed a terrifying truth: the U.S. air traffic control system was dangerously outdated, relying on pilots' visual estimates and rough guesswork from controllers , with no way to separate fast-moving aircraft from slow ones, or instrument-flying planes from those navigating by sight. Congress responded by passing legislation that created both the Federal Aviation Administration (FAA) and the National Transportation Safety Board.

4

A hoax suggested that an Egyptian civilization had lived there

In 1909, the Arizona Gazette reported that an explorer named G. E. Kinkaid had discovered a vast underground citadel inside the canyon, filled with artifacts linked to ancient Egyptian civilization. He even claimed the expedition had been funded by the Smithsonian.

This story described hieroglyphics on the walls, mummies in the chambers, and relics pointing to a direct connection with the Egypt of the pharaohs. It was incredibly detailed, and it was, of course, a hoax. No evidence for any of Kinkaid's claims ever surfaced.

5

Fewer than 100 people have ever hiked its full length

Among the few people who have completed the through-hike of the Grand Canyon is Jen Hogan, the first woman to accomplish it, finishing her journey in 2021–2022.

It’s a full 800-mile length below the rim. The route involves extreme heat, flash floods, near-impassable areas, and stretches with no water or trail whatsoever. Around 60 or 70 people have reportedly accomplished it. This makes it one of the most exclusive feats on Earth.

6

The Grand Canyon's rocks predate dinosaurs entirely

Visitors scanning the canyon walls for fossils are often surprised to learn they won't find any dinosaur bones here. The rock layers of the Grand Canyon are simply older than dinosaurs. This fact alone can be shocking: staring at its walls means staring at marine fossils from as far back as 1.2 billion years ago. Some of its caves hold the remains of ancient mammals. The canyon is a window into a world that existed long before the dinosaurs, when the land that is now Arizona lay beneath a shallow sea.

7

The park is bigger than Rhode Island

Numbers alone rarely capture the Grand Canyon's scale, so here's a different approach. Rhode Island covers about 1,214 square miles, and the Grand Canyon National Park spans 1,904 square miles.

The canyon's depth exceeds four Empire State Buildings (which is 1,454 feet) stacked on top of one another. That’s 6,093 feet at its deepest point.

8

But it's not the deepest canyon on Earth

For all its grandeur, the Grand Canyon does not hold the depth record. Pictured above, the Yarlung Tsangpo Grand Canyon in Tibet, China, plunges to 17,567 feet, which is nearly three times deeper. Carved by the Yarlung Tsangpo River as it cuts through the eastern Himalayas, that canyon is so remote and extreme that it remained largely uncharted until the late 20th century.

9

It is home to a pink rattlesnake found nowhere else on Earth

The Grand Canyon Pink Rattlesnake has a pinkish-red coloring that matches the canyon's own distinctive rock walls so closely that it's nearly invisible. It is found nowhere else in the world. Officially classified as Crotalus oreganus abyssus , it has darker diamond-shaped markings along its back that deepen the camouflage further.

10

There's a village at the bottom: Supai Village

For over 1,000 years, the remote village of Supai has been home to the Havasupai Tribe, the People of the Blue-Green Waters. It is located an eight-mile hike from the rim, but sits roughly 3,000 feet deep inside the Grand Canyon.

The U.S. Department of Agriculture has called it the most remote community in the contiguous United States, and it has no automobiles and no road access. The only ways in are on foot, by mule, or by helicopter. It is also the only place in the United States where the postal service still delivers mail by mule train.