1

The Great Chicago Fire (1871)

Image: Ricardo Gomez Angel

The Great Chicago Fire burned for almost two days in October 1871, destroying thousands of buildings and leaving the city in ruins . Sparks, dry conditions, and wooden construction helped the flames race through entire neighbourhoods.

It was a painful turning point, but it launched a huge rebuilding effort. Chicago adopted tougher building codes, better water systems, and more specialized fire departments, becoming a model city for urban planning.

2

The Johnstown Flood (1889)

Image: Lukas Hron

In 1889, the failure of the South Fork Dam sent a massive wall of water toward the town of Johnston, Pennsylvania . The flood wiped out entire homes, bridges, and rail lines in a matter of minutes.

The Johnstown Flood drew attention to private dam ownership and safety inspections of such constructions. Engineers and lawmakers used its lessons to plan for better maintenance and more accountability for these large-scale structures.

3

The San Francisco Earthquake (1906)

Image: Library of Congress

The 1906 San Francisco earthquake struck before dawn, violently shaking the city and the surrounding areas . Broken gas lines and toppled chimneys sparked fires that raged for days , destroying block after block of homes and businesses alike.

Rebuilding was hard but transformative, as the city adopted stricter building codes, stronger materials, and better street layouts.

4

Triangle Shirtwaist Factory Fire (1911)

Image: Pukima ‎

The Triangle Shirtwaist Factory Fire of 1911 began on the upper floors of a New York City garment factory packed with workers. Locked exit doors, narrow stairways, and crowded conditions turned what would have been a relatively small blaze into a historic tragedy.

Public outrage was immediate and intense. The fire led to tough new safety laws, regular inspections, and rules for unlocked exits and fire escapes.

5

The Hindenburg Disaster (1937)

Image: Library of Congress

In 1937, the German airship Hindenburg approached its mooring mast in Lakehurst, New Jersey, after a transatlantic flight. Suddenly, it burst into flames and fell to the ground in front of cameras and radio reporters who witnessed the tragedy.

The disaster shocked the world and quickly ended the age of passenger airships. Public trust shifted toward airplanes, and the whole airship industry faded into obscurity almost completely.

6

The Texas City Disaster (1947)

Image: Ash Edmonds

The Texas City Disaster of 1947 began when a ship carrying ammonium nitrate caught fire in the bustling Texas City harbor . As crowds watched from the waterfront, the cargo exploded in a blast so powerful it shattered windows miles away.

The incident prompted sweeping changes in how hazardous materials are stored, transported, and labeled. It led to improved emergency planning, better first-responder training, and regulations aimed at preventing industrial catastrophes.

7

The Silver Bridge Collapse (1967)

Image: Suzanne Anderson

On a 1967 December day, the Silver Bridge that connected Point Pleasant in West Virginia to Gallipolis, Ohio, collapsed into the river below . Dozens of vehicles were on the bridge and fell into the water.

The collapse spurred nationwide inspections of older bridges and stricter design standards. It introduced new rules for maintenance, record keeping, and modern safety ratings.

8

Buffalo Creek Flood (1972)

Image: Chris Gallagher

In 1972, after days of heavy rain, a coal-waste dam above Buffalo Creek, West Virginia, gave way . A torrent of water and slurry rushed down the narrow valley, wiping out homes, roads, and small communities in its path.

The Buffalo Creek Flood drew national attention to the dangers of poorly regulated waste dams, and it helped push stricter environmental laws across the country.

9

Three Mile Island (1979)

Image: Lee Lawson

The Three Mile Island accident of 1979 began with equipment failures followed by human mistakes inside a nuclear power plant . Cooling problems led to a partial meltdown of the reactor core, alarming nearby residents and the entire country.

Even though it was contained, the incident reshaped nuclear energy in America. Regulators tightened training, communication, and emergency procedures.

10

Hyatt Regency Walkway Collapse (1981)

Image: AJOY DAS

The Hyatt Regency walkway collapse in Kansas City happened during a popular social dance event in 1981. Two suspended walkways above the hotel lobby suddenly gave way, crashing onto the crowded area below .

Investigations exposed serious flaws in the design and in the approval process itself. The disaster led to stricter engineering reviews, clearer responsibilities, and tougher building codes.

11

Exxon Valdez oil spill (1989)

Image: Yuval Zukerman

The Exxon Valdez tanker struck Bligh Reef in Alaska’s Prince William Sound in 1989, tearing open its hull. Crude oil spilled into the cold waters , drifting onto beaches, shorelines, and wildlife habitats in the surrounding area.

The spill led to new rules for double-hulled tankers, improved navigation systems, and better emergency response plans. It also inspired major environmental legislation and long-term monitoring to reduce the impact of future shipping incidents.

12

Deepwater Horizon (2010)

Image: Jonathan Gong

In April 2010, the Deepwater Horizon drilling rig experienced a blowout during exploratory drilling . A series of failures led to an explosion and a major well leak far below the ocean’s surface, drawing worldwide attention.

The disaster sparked new offshore drilling rules, better blowout preventers, and stricter inspection routines. It also sparked debates about energy policies and environmental protection.

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.