Two hundred and fifty years ago this week, a group of delegates in Philadelphia signed their names to the Declaration of Independence. Today, we are going to talk about how chemistry made it all possible.

Let's start at the beginning. 1776.

When the Continental Army took the field against the British, they faced a big problem: they were running out of black powder.

Black powder, the mixture of potassium nitrate, charcoal, and sulfur that had been the world's only practical explosive for nearly a thousand years,  was the lifeblood of 18th-century warfare. Without it, muskets were clubs and cannons were lawn ornaments.

The British knew this. One of their first strategic moves was to cut off American access to gunpowder imports.

The Continental Congress responded by establishing saltpeter works across the colonies — saltpeter being potassium nitrate, the critical oxidizer in black powder. Farmers were encouraged to collect it from barn floors, from caves, from anywhere nitrogen-rich organic matter had decomposed. It was unglamorous, essential chemistry.

Fast forward to 1802. A French immigrant named Éleuthère Irénée du Pont de Nemours purchased land along the Brandywine Creek in Delaware, and built a gunpowder mill.

E.I. du Pont had trained under the great French chemist Antoine Lavoisier, the father of modern chemistry, and he brought that rigor to American manufacturing. His powder was more consistent, more powerful, and safer to produce than anything made domestically at the time.

The timing was not coincidental. The new American government needed a reliable domestic supplier. The War of 1812 was barely a decade away. DuPont's Brandywine mill would supply powder for that war, and for every major American military conflict for the next hundred years.

What's remarkable about DuPont's early story is how clearly it illustrates the relationship between chemistry and national power. The company didn't start as a chemical conglomerate. It started as a single product solving a single critical problem: America could not afford to run out of explosives again.

By the Civil War, DuPont was supplying roughly half of all the gunpowder used by Union forces. Half. One company. On the Brandywine Creek in Delaware. That's the kind of industrial concentration that happens when you get the chemistry right early.

The Civil War also pushed American explosive chemistry in a new direction because black powder, for all its history, had real limitations. It was bulky. It left enormous clouds of white smoke. And it wasn't nearly powerful enough for the engineering challenges of the 19th century:  blasting railroad tunnels through the Appalachians, cutting canals, moving mountains of rock.

Enter nitroglycerin, and then dynamite. Alfred Nobel stabilized nitroglycerin with diatomaceous earth in 1867, and American industry seized on it. The expansion of the railroad network westward was, in no small part, a chemistry story. Dynamite made it possible to do in days what would have taken months with black powder.

DuPont acquired dynamite manufacturing capacity and, by the turn of the 20th century, had evolved from a gunpowder company into a full-spectrum explosives and chemical enterprise. They controlled roughly two-thirds of the U.S. explosives market by 1902, which eventually attracted the attention of antitrust regulators. The government sued under the Sherman Act, and in 1912 DuPont was ordered to spin off two competitors: Hercules and Atlas Powder.

But that breakup, ironically, seeded the ground for even more innovation. Three explosives companies where there had been one. All of them well-capitalized, technically sophisticated, and about to face the greatest chemical challenge in human history.

And DuPont wasn't alone in that story. Out in Midland, Michigan, a young chemist named Herbert Dow had founded his own company in 1897, built around electrolytic extraction of bromine from underground brine deposits. Dow Chemical was small compared to DuPont, but technically fearless. That combination would prove critical in the decades ahead.

World War One changed everything.

Before 1914, no one truly understood what industrial-scale warfare looked like. Within months of the war's outbreak, it became clear: this was going to be a chemical war in ways no one had anticipated.

The most urgent problem on the Allied side was high explosives, specifically TNT and picric acid, which required massive quantities of toluene and phenol. These were coal-tar derivatives, and American chemical companies scrambled to scale up production from almost nothing.

But the deeper problem was nitrogen. Explosives require nitrogen. Fertilizers require nitrogen. And the world's supply of fixed nitrogen — mostly from Chilean sodium nitrate — was finite and, in wartime, controlled. Germany had a massive strategic advantage here because German chemists Fritz Haber and Carl Bosch had, just years earlier, developed a process to synthesize ammonia directly from atmospheric nitrogen. The Haber-Bosch process. It is, arguably, the most consequential chemical invention in history, it underpins the fertilizers that feed roughly half the world's population today.

When America entered the war in 1917, the government essentially nationalized the problem. A massive synthetic nitrogen fixation plant was built at Muscle Shoals, Alabama. DuPont was contracted to build and operate a smokeless powder facility of staggering scale. American organic chemistry, which had lagged far behind Germany's for decades, was suddenly a matter of national survival.

The war lasted only another year after American entry, but the chemical infrastructure built to fight it didn't disappear. It transformed. The engineers and chemists who had learned to synthesize complex organic molecules at scale looked at peacetime and saw possibilities everywhere.

Which brings us to the interwar years, and perhaps DuPont's greatest chapter.

Armed with wartime expertise, government contracts, and the cash generated by powder sales, DuPont invested heavily in fundamental research. They acquired a dye company, moved into synthetic materials, and hired a Harvard chemist named Wallace Carothers to lead a new research station in Wilmington.

What Carothers and his team produced in that lab in the 1930s would reshape modern life. Neoprene, the first truly successful synthetic rubber. And then, in 1935, nylon, the world's first fully synthetic fiber, made from coal, water and air.

Nylon stockings went on sale in 1940. Women lined up around the block.

And then Pearl Harbor happened, and every strand of nylon in America went to the war effort. Parachutes. Rope. Tires. Flak jackets. The same polymer that had seemed like a luxury product became military-critical infrastructure overnight.

World War Two was, more explicitly than any conflict before it, a war of chemistry. And this time, it wasn't just DuPont carrying the load. It was the entire American chemical industry, mobilized at a scale never seen before or since.

Take synthetic rubber. When Japanese forces swept through Southeast Asia in 1941, they cut off Allied access to 90 percent of the world's natural rubber supply. Overnight, rubber became a war-critical material. The U.S. government launched one of the largest crash programs in industrial history, and Dow Chemical was at the center of it, producing the magnesium used in aircraft frames and incendiary devices, while companies like Standard Oil of New Jersey contributed the petroleum-derived butadiene that was the backbone of the new synthetic rubber, Buna-S. Within three years, America had built synthetic rubber production capacity from near zero to over 700,000 tons per year. That is what industrial chemistry looks like when a nation decides it has no other option.

Aviation fuel tells a similar story. Standard Oil's chemists had been developing catalytic cracking and alkylation processes through the 1930s, and those processes made possible 100-octane aviation gasoline, fuel that gave Allied fighter engines dramatically more power than their opponents. The fuel in a Mustang's tank was as much a weapon as the guns on its wings.

And then there was the Manhattan Project, the most concentrated application of chemistry and physics in history, producing a weapon that ended the war and inaugurated the atomic age. DuPont built and operated the Hanford plutonium production facility in Washington State, scaling a nuclear reactor from laboratory prototype to full industrial production in roughly two years. Meanwhile, Tennessee Eastman, the industrial division of Kodak, operated the massive K-25 gaseous diffusion plant at Oak Ridge, Tennessee, enriching uranium through a process that had never been done at anything approaching that scale. Eastman also ran the Holston Ordnance Works, producing RDX, the most powerful conventional explosive of the war.

A film company. Running one of the most sophisticated uranium enrichment facilities in human history. That sentence alone tells you something remarkable about what American industry was capable of when pushed.

From saltpeter on barn floors in 1776 to plutonium production in 1944, American chemistry has always developed in response to need. 

The Revolution revealed a dependency on foreign powder. DuPont filled that gap. The Civil War demanded scale. American industry delivered. World War I exposed how far behind American chemistry had fallen. The crisis accelerated a generation of catch-up. World War II demanded the impossible. DuPont, Dow, Standard Oil, Tennessee Eastman, Hercules and dozens of companies you've never heard of built it anyway, together.

Two hundred and fifty years ago, the founders signed a declaration. They were betting everything on a nation that didn't yet exist, fighting a war they had no guaranteed way to win. What they had, besides courage and conviction, was resourcefulness. The ability to solve the problem in front of them with whatever was at hand — or to build what wasn't.

So this Fourth of July, when you watch the fireworks and see those bright bursts of color, each one a small, precise chemical reaction converting strontium salts and oxidizers and metal powders into light, take a moment to appreciate what you're seeing. It's not just a celebration of American independence.

It's chemistry, put to its most spectacular use. Two hundred and fifty years in the making.

Happy Fourth, everyone. Thanks for listening to Distilled.