Dave Roos

Incredibly, there are roads dating back millennia that are still in use.

Printed just weeks after British troops opened fire on an unarmed crowd of Bostonians, Revere’s depiction of the melee likely stoked anti-British sentiment throughout the colonies.

The 1798 Alien and Sedition Acts called for deportation of people from 'hostile' nations and made it a crime to criticize the government.

With the Aqua-Lung, the French oceanographer and filmmaker realized his dream of creating a system to swim and breathe freely underwater.

The remarkable cliff dwelling in Arizona was occupied for nearly 300 years. New studies combined archaeological data with oral history to figure out why everyone left.

Before the Department of Defense, the U.S. had a Department of War and a National Military Establishment.

That classic boxcar design evolved from horse-drawn wagons.

The attacks of 9/11 shocked the nation—and led to changes that altered U.S. government, travel and culture.

Eisenhower installed 'elevator music' in the White House and NASA used it in astronaut training, but its inventor came up with many other, more impactful inventions in his lifetime.

Electric vehicles were some of the earliest automobiles ever invented—and, unlike early gas-powered cars, they didn't require a crank to start the engine.

They have actually been around since ancient times.

Lamarr was a glamorous movie star by day, but she was also a gifted, self-trained inventor who developed a technology to help sink Nazi U-boats.

Some of the modern world's most groundbreaking technologies emerged during this 30-year period.

In the first half of the 20th century, U.S. educators shunned homework. The Soviet Union’s launch of Sputnik 1 changed that.

The Posse Comitatus Act addressed Southern politicians' objections to military enforcement of Reconstruction following the Civil War.

Flag burning has long tested the limits of freedom of speech.

A 40-hour, five-day work week is now standard for full-time jobs in America, but that wasn't true until the 1930s.

The once-great empire on the Nile was slowly brought to its knees by a centuries-long drought, economic crises and opportunistic foreign invaders.

In Plato's 'Republic,' the ancient Greek philosopher lays out five different forms of government, ranging from ideal to oppressive.

When the Mississippi River broke through a manmade embankment, it triggered a 48-day flood that changed the way New Orleans managed its levees.

This teenage 'puppet' emperor ruled for 10 months.

Since 1990, the world's top codebreakers have been stumped by a mysterious sculpture called 'Kryptos.'

The luxury liner’s collision with an iceberg set off a tragic chain of events.

Artificial flies were first mentioned in 200 A.D., but the sport really took off in the 1800s.

From desegregation at Little Rock to MLK's Selma-to-Montgomery march to the Cuban refugee crisis, these are major moments when U.S. presidents have deployed troops in America.

From the Civil War to the rule of Ferdinand Marcos in the Philippines, find out how martial law has been enforced—and exploited.

Hear about the harrowing days of Hurricane Katrina from people who were there—helicopter rescue workers, Superdome survivors and unlikely heroes.

From axes to swords to chariots, see the weapons that helped make ancient Egyptian warriors formidable.

The 13th-century pact inspired the U.S. Founding Fathers as they wrote the documents that would shape the nation.

Legendary warrior chief was first Hawaiian to travel the world.

Elite Gilded Age families competed for status by building extravagant summer 'cottages' in Newport and throwing lavish parties.

Colorado claims 18 of the 20 highest towns in the United States, but not the highest state capital.

Roosevelt's heroism at the Battle of San Juan Hill was the culmination of years of conscious personal transformation and myth-making.

The tsunami was the deadliest in recorded history, taking 230,000 lives in a matter of hours.

Rotten meat swarming in fly larvae was likely a major component of the ancient hominin diet, says a new study.

Our human ancestors' big, creative brains helped them devise tools and strategies to survive harsh climates.

A single giant sequoia could supply 500,000 board feet of lumber, a bonanza for profit-hungry logging companies—or so it was thought.

In 1804, Lewis and Clark set off on a journey filled with harrowing confrontations, harsh weather and fateful decisions as they scouted a route across the American West.

Indigenous people routinely burned land to drive prey, clear underbrush and provide pastures.

Hungry bears—whether grizzly, black, brown or polar—can be shockingly brutal.

Feeling the heat? See if you're living in one of the historically steamiest states in the country.

The exact location of the ancient, gnarled bristlecone pine is kept secret for its protection.

The longest cave system winds for more than 400 miles, but others on the list haven't even been fully explored yet.

On the heels of the Great Depression, the federal government under FDR hired young people to work on projects across the country. Here’s what the Corps got done.

The explorers not only produced maps from their 1804-1806 expedition to the American West, they also recorded some 122 animals new to science.

There have always been daredevils. But never has there been such a variety of creative ways to defy death—and break a few world records along the way.

The Yippies found their voice by organizing an absurdist counter-convention—including nominating a pig for president.

The Allied invasion of Normandy was among the largest military operations ever staged.

The L.A. Aqueduct was celebrated as an engineering marvel at its completion in 1913, but it drained distant watersheds for the city's own precarious supply.

From the Space Needle to the Atomium, these landmarks stand as remarkable legacies of 19th- and 20th-century global exhibitions.