1

Postal "Army" (of Sorts)

Image: Emily Powers

The U.S. Postal Inspection Service (USPIS), founded in 1775, is the nation’s oldest federal law enforcement agency . It protects the USPS, its employees, and its customers from crimes such as mail fraud, theft, and identity theft.

USPIS agents investigate mail-related crimes, provide security at postal facilities, and work to stop illegal drugs from being transported through the mail system.

2

Zip codes

Image: Tareq Ismail

ZIP codes were introduced by the USPS in 1963 to improve mail sorting and delivery. The five-digit code, short for Zone Improvement Plan, pinpoints specific geographic areas.

The digits represent a region, a city or county, and a local delivery zone . Today, ZIP codes are also used to study demographics and help businesses target mailings to particular areas.

3

The Postal Anthem

Image: Keagan Henman

The "United States Postal Service Anthem," composed by Jack Stamp (yes, that is his real name), honors the USPS and its long-standing service to the nation. It’s a musical tribute to the dedication of postal workers and the agency’s role in American life.

The lyrics highlight the USPS’s core values: honesty, integrity, and reliability, while celebrating its impact on U.S. history and everyday citizens.

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4

Guaranteed delivery

Image: Victória Kubiaki

The USPS is legally required to deliver to every U.S. address, no matter how remote . This includes over 153 million addresses, even in hard-to-reach areas.

To meet this huge challenge, USPS uses curbside mailboxes, local post offices, and partnerships with community centers. Virtual mailbox services, such as Stable, also help remote residents access and manage their mail online.

5

A lot of mail

Image: Sam LaRussa

Every day, the USPS handles over 400 million pieces of mail, including 162 million First-Class items. It delivers worldwide to more than 180 countries through its Global Express Guaranteed service and processes approximately 44% of the world’s mail . That is a lot of mail, by any standard.

To manage this massive volume, USPS uses advanced automation tools and operates over 34,000 retail locations, keeping its system fast, efficient, and reliable.

6

Going out West

Image: Jim Strasma

In the 19th century, the USPS played a vital role in developing the American West, providing new settlements with access to mail, supplies, and communication. Post offices and mail routes connected remote areas to the rest of the country.

This network helped settlers stay in touch with loved ones, receive news, and trade goods. Without the USPS, much of the frontier would have remained isolated.

7

Post office in a tavern

Image: Kevin Snow

‍ The first USPS office was established in Boston in 1775, inside a tavern associated with Benjamin Franklin , who served as the first Postmaster General. Franklin viewed mail delivery as key to America’s independence and began developing a postal network.

The office supported routes to Philadelphia and New York, and by 1789, post offices existed in all 13 colonies.

8

A floating post office

Image: Alessio Billeci

The Halibut Cove Post Office in Homer, Alaska (ZIP code 99603, in case you are interested), is unlike any other: it floats on water!

This tiny post office operates from a houseboat that’s permanently docked , serving the local community right from the harbor.

9

Bad handwriting department

Image: Kit (formerly ConvertKit)

We are not sure as to how often this happens, but it must be often. When automated equipment at a USPS processing plant cannot read a piece of letter mail, an image of the mail is captured and sent to the Remote Encoding Center (REC). At the REC, employees review the image and manually enter the address information .

The information is matched up with a valid address, the data is transmitted back to the equipment at the plant, and a barcode is printed on the letter, which can be read by the processing machines.

10

Mail a brick

Image: Math

Yes, you can mail a brick through the U.S. Postal Service. Just write the recipient’s address and return information directly on the brick with a permanent marker .

Once it’s weighed and stamped with the correct postage, your brick is ready to ship.

11

Someone mailed a kid

Image: Jonathan Borba

In 1913, shortly after the Parcel Post service began, some parents mailed their children to relatives. One baby in Ohio was sent to his grandmother just a few miles away .

The child arrived safely, but the incident led to new rules banning people from being sent through the mail.

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.