**** THE GREAT GUANO MADNESS **** The Forgotten Scramble That Gave America Its Imperial Playbook

Picture this: It's 1856, and the United States Congress—the same body that would soon wrestle with the impending Civil War—is deadly serious about bird poop. So serious, in fact, that they're about to pass legislation that will fundamentally reshape American territorial expansion. So serious that they'll send naval warships to protect it. So serious that claims of "finders keepers" on remote Pacific rocks will stand up in the Supreme Court.

Welcome to the Guano Age, perhaps history's strangest gold rush.

An Ancient Secret Rediscovered

The word "guano" comes from the Quechua word huanu, meaning dung. And for the Inca Empire—possibly the largest empire in the world in the early 16th century—this wasn't just fertilizer. It was the foundation of their civilization.

The Inca had been harvesting seabird guano for potentially 5,000 years, using it to transform the nutrient-poor soils of their vast territory into farmland that could feed over eight million people. They understood its power so completely that they created elaborate regulations: each province was assigned specific islands, each household received its share based on need, and anyone who killed a guano-producing bird or even landed on an island during breeding season faced execution. The punishment for disturbing the resource? Death. The Inca didn't mess around when it came to bird poop.

When Spanish conquistadors arrived in the 1500s, they noticed the indigenous people using "no other manure but the dung of sea birds," which created heaps that from a distance looked like "the snowy crests of a range of mountains." But blinded by shinier commodities—gold, silver—the Spanish largely ignored it for centuries.

Then came Alexander von Humboldt, the Prussian geographer, in 1802. While conducting celestial observations in Lima, he spent his days wandering the docks and couldn't stop sneezing from the ammonia-rich guano being loaded onto ships. When he asked about it, his hosts insisted it was made by seabirds. Humboldt was skeptical—there was just too much of it—but its fertilizing power was undeniable. He brought samples back to Europe in 1804, and "the best analytic chemists of the day" immediately recognized they were dealing with something extraordinary.

Around the same time, English chemist Humphry Davy was delivering lectures on agricultural chemistry, which became a bestselling 1813 book that highlighted the special efficacy of Peruvian guano, noting it made the "sterile plains" of Peru fruitful. The secret was out.

The White Gold Rush

By the 1850s, American and European farms were dying. Decades of intensive agriculture had sucked the life from the soil, and farmers were desperate for a solution. Guano—the accumulated droppings of pelicans, cormorants, and boobies—proved to be agricultural dynamite. This wasn't just good fertilizer; it was transformative. American tobacco and produce farmers who applied Peruvian guano to their fields saw crop yields triple. Triple.

Peru had the best stuff, thanks to one crucial factor: it never rained there. The Humboldt Current carries cold, nutrient-rich Antarctic waters up the Peruvian coast, creating a vibrant aquatic ecosystem where millions of seabirds feast on anchovies and deposit their nitrogen-rich droppings. While rain would wash away nitrogen elsewhere, Peru's coastal climate preserved guano deposits that had accumulated for millennia—sometimes reaching 150 feet deep—creating literal mountains of the finest natural fertilizer the world had ever seen. The British were importing over 200,000 tons annually. Americans? A staggering 760,000 tons.

And here's what made it truly valuable: guano wasn't just fertilizer. It was also a key ingredient in explosives. Every nation considered it a strategic commodity—you needed it both to feed your people and to arm them.

There was just one problem: Peru controlled the supply, prices were astronomical, and American farmers—never a patient bunch—were howling for their government to do something about it. In his 1850 State of the Union Address, President Millard Fillmore spent an entire paragraph on "tough talk," committing to do anything necessary to make Peruvian guano available to American farmers.

Congress answered in 1856 with one of the most audacious pieces of legislation in American history: the Guano Islands Act.

What Exactly Is the Guano Islands Act?

The law was breathtaking in its simplicity. Any American citizen who discovered an unclaimed island containing guano deposits could claim it in the name of the United States. Think about that for a moment: individual private citizens could expand American territory.

No bureaucracy, no diplomatic negotiations, no purchase necessary. Just plant a flag and file the paperwork. The President would back your claim with military force. U.S. criminal law would apply to these islands—they became American territory in every legal sense. And here's the kicker: once you'd scraped the island clean of guano, America could just... walk away. No obligation to keep it.

The Act created something entirely new in American jurisprudence: insular, unincorporated territories. These were places under U.S. jurisdiction but not part of any state, not destined for statehood, existing in constitutional limbo. They weren't intended for American settlement—they were purely extractive ventures, colonial possessions with an expiration date.

Senator William H. Seward (yes, the same Seward who would later orchestrate the Alaska Purchase) championed the Act, arguing that American agriculture couldn't be held hostage to foreign guano cartels. Congress agreed overwhelmingly. After all, what could possibly go wrong with telling American entrepreneurs they could claim any rock they stumbled upon in the Pacific?

The Scramble

What followed was bedlam.

Within just a few years, Americans filed claims on nearly 200 islands, rocks, atolls, and barely-submerged reefs scattered across the Pacific and Caribbean. The U.S. Navy found itself mobilized to the far corners of the ocean, protecting American guano miners from rival claimants, angry islanders, and occasionally from each other.

Baker Island became the first claim in 1857—a flat, sun-scorched speck of coral in the middle of nowhere, but it had guano, and that made it American.

The competition got fierce. When Peter Duncan and Edward Cooper discovered that Navassa Island—just off Haiti's coast—was sitting on a million tons of guano in 1857, Haiti protested that the island was theirs. America claimed it anyway. Haiti objected. America sent gunboats. Navassa became American.

Even the Smithsonian got involved. When the USS St. Mary's collected guano samples from New Nantucket and Jarvis islands in 1857, they shipped them back to Washington where Joseph Henry, the Smithsonian's first Secretary, personally analyzed their nitrogen content. The nation's premier scientific institution was now in the bird poop evaluation business.

The Ugly Side

This wasn't some victimless caper. The guano islands became sites of brutal labor exploitation. Workers—often recruited from Caribbean nations or China under dubious circumstances—toiled in hellish conditions under the blazing sun, breathing ammonia-laden air that burned their lungs, mining deposits that had taken thousands of years to accumulate.

From 1840 to 1870, an estimated 12 million tons of guano were extracted from Peru's islands alone. The work was backbreaking and toxic. Many workers were essentially enslaved—Chinese, Polynesian, and Easter Islanders were shanghaied or deceived into contracts they couldn't escape. During the height of the boom in the mid-19th century, the work was done by prisoners and Chinese indentured servants under brutal conditions, many of whom perished on the islands.

On Navassa, conditions got so bad that in 1889, Black American workers revolted, killing their overseers. Five men were tried, convicted of murder, and sentenced to death (later commuted). The incident sparked a legal battle that reached the Supreme Court, which used the case to affirm that yes, these random rocks really were U.S. territory, and yes, American law really did apply there.

Ecologically, the impact was catastrophic. At the peak of guano mining, estimates suggest that Peru's coasts and islands were home to some 53 million seabirds. By 2011, the population had plummeted to just 4.2 million—a loss of over 90% of the bird population. The constant human disturbance during the nineteenth century meant breeding grounds were disrupted year after year. Seabirds are relatively long-lived and typically have only one or two eggs a year, so continuous disturbance of breeding sites meant populations couldn't recover.

The destruction went beyond just disturbing the birds. In 1913, Scottish ornithologist Henry Ogg Forbes authored a report detailing how human actions harmed the birds and subsequent guano production, recommending that unauthorized visitors be kept a mile away from guano islands at all times, that all the birds' natural predators be eliminated, and that harvest frequency on each island be decreased to once every three to four years. The damage was so severe that even with these protections, the populations never fully recovered.

But there was an even more insidious threat: other nations realized they could "cut out the middleman"—the birds themselves—by catching the fish the seabirds were eating and processing them directly into fertilizer. The result was a massive crash of Peruvian seabird populations as birds simply starved. Overfishing of anchovies, the seabirds' primary food source, combined with El Niño events that disrupted the Humboldt Current's nutrient-rich upwelling, caused periodic mass die-offs of millions of birds.

America's Parallel Imperial Land Grab

The timing of America's guano rush wasn't coincidental. It was happening at almost the exact same moment as Europe's far more famous Scramble for Africa.

In the 1880s—just as Americans were planting flags on Pacific rocks for bird droppings—European powers were carving up an entire continent. Between 1880 and 1914, European control of Africa went from 10% to 90%. The parallels are striking and disturbing.

Both territorial grabs were driven by resource extraction. Africa had gold, diamonds, rubber, ivory, and other raw materials vital to industrial economies. The Pacific had guano. Both were justified by pseudo-legal frameworks: the 1884-85 Berlin Conference for Africa (where not a single African was present), and the Guano Islands Act for the Pacific (where no Pacific Islander had a voice). Both created territories that were under imperial control but not destined for integration into the metropole—extractive colonies, pure and simple.

Both races for territory featured the same players muscling their way into the imperial game. Germany, Italy, and Belgium—newly unified or newly ambitious nations seeking to prove their status as "great powers"—joined established empires like Britain and France in the feeding frenzy. Germany was acquiring territories in Africa (Southwest Africa, Togoland, Cameroon, Tanganyika) while Americans were claiming Pacific islands. The timing wasn't coincidental: this was the age of "New Imperialism," when industrial nations competed ferociously for global resources and strategic positions.

Both scrambles also featured the same technological advantages: Europeans used maxim guns (which could fire 500 rounds per minute) and steamships to conquer Africa; Americans used naval power to seize and defend guano islands. Both exploited local populations ruthlessly. And both scrambles rewrote maps and created lasting territorial arrangements that persist today.

The difference? Scale and lasting impact. The Scramble for Africa shaped the entire 20th century, created artificial borders that fuel conflicts to this day, and resulted in the deaths of millions (in the Congo alone, colonization claimed 10 million lives). The Guano Scramble was smaller, briefer, and involved mostly uninhabited rocks. But the logic was identical: powerful nations claiming distant territories for resource extraction, using legal frameworks that gave colonized peoples no voice, justified by ideas of civilizational superiority and economic necessity.

Peru, Bolivia, and Chile even fought their own war over guano and saltpeter* resources—the War of the Pacific (1879-1883)—which left as many as 18,000 dead. Bolivia lost its entire coastline and remains landlocked to this day. By the war's end, Chile controlled "the most valuable nitrogen resources in the world," and Chile's national treasury grew by 900% between 1879 and 1902 thanks to taxes from these newly acquired lands.

The uncomfortable truth: America's guano adventure established the legal and political framework for a century of American imperialism in the Pacific and Caribbean—territories like Puerto Rico, Guam, American Samoa, and the U.S. Virgin Islands all exist in the same constitutional limbo first created for bird-poop islands.

*Saltpeter (also known as niter or potassium nitrate) is another naturally occurring nitrogen compound found in arid climates, often in the same regions as guano. Like guano, it was crucial for making both fertilizers and explosives, which is why nations fought wars over it.

When the Party Ended—And What Replaced It

Just as suddenly as it began, the guano craze collapsed. By 1880, the easily accessible deposits were exhausted. Seabird colonies whose ancestors had created these mountains of fertilizer over millennia couldn't possibly replenish them fast enough to meet industrial demand.

But more importantly, guano was being replaced by something even better: synthetic fertilizers. And this is where the story takes a fascinating turn into the realm of world-changing chemistry.

In 1856—the exact same year as the Guano Islands Act—German chemists were racing to solve what they called "the nitrogen problem." Scientists were warning that natural sources of nitrogen (guano, Chilean saltpeter) would soon run out, and millions would starve. By the turn of the century, with global population soaring, the crisis seemed imminent. Sir William Crookes, head of the British Academy of Sciences, warned in the 1890s that the world was heading for mass famine—a true Malthusian catastrophe—unless someone discovered how to synthesize fertilizer from thin air.

Enter Fritz Haber, a German chemist who in 1909, working with his student Robert le Rossignol, figured out how to combine nitrogen from the air with hydrogen under extreme pressure and temperature to create ammonia. It was a tabletop contraption that produced ammonia drop by drop over two hours—hardly impressive—but it worked.

The German chemical company BASF saw the potential and assigned engineer Carl Bosch to scale it up. By 1913, just as the last guano islands were being scraped clean, BASF opened the first industrial ammonia plant in Oppau, Germany. The Haber-Bosch process, as it became known, could pull nitrogen directly from the atmosphere (which is 78% nitrogen) and turn it into fertilizer. The process was revolutionary, eventually earning both men Nobel Prizes.

The timing was darkly fortuitous. When World War I broke out in 1914, Britain blockaded Germany, cutting off access to Chilean saltpeter—vital for making explosives. Without the Haber-Bosch process producing synthetic ammonia, Germany would have run out of ammunition within months, and the war would have been considerably shorter. Instead, the same factories making fertilizer simply switched to making explosives, and the war dragged on for four more years.

After the war, attention turned back to feeding people. By the 1950s, the Haber-Bosch process was being used to produce nitrogen fertilizers on a massive scale. Today, the process produces about 450 million tons of ammonia annually. It's estimated that nearly half the nitrogen in your body came from the Haber-Bosch process. Without it, we'd need roughly four times more farmland to feed the current global population, and we'd have converted half of all ice-free continents to agriculture.

So the guano craze ended not because the need disappeared, but because humanity figured out how to manufacture what nature had taken millennia to produce. Bird poop was replaced by industrial chemistry. The Guano Islands became obsolete almost overnight.

But is where the story gets even stranger: America didn't give them back. Instead, these forgotten outposts became something else entirely—military installations, naval refueling stations, strategic positions in an increasingly militarized Pacific.

Midway Atoll, claimed for its guano in 1867, became the site of one of World War II's most decisive battles. Wake Island became a military base. Johnston Atoll was transformed during the Vietnam War into a storage and incineration facility for chemical weapons, including Agent Orange. Howland Island became famous not for guano but as the place Amelia Earhart never reached.

The Legacy of Bird Shit

Nine of these guano islands remain U.S. territories today, scattered across the Pacific like America's strangest footnote. They're unincorporated, unorganized, and mostly uninhabited. The Guano Islands Act remains on the books, theoretically still in effect, though the last successful claim was filed in 1935.

What makes the whole episode historically significant ? The Act established the legal framework for America's "insular territories"—places under U.S. jurisdiction but not part of any state, not destined for statehood, existing in constitutional limbo. This legal innovation would later justify U.S. control over Puerto Rico, Guam, American Samoa, and the U.S. Virgin Islands. The template for American empire in the 20th century was invented to facilitate the harvest of bird droppings.

The 1890 Supreme Court case Jones v. United States confirmed that discovering a guano island was enough to make it American, establishing precedents about sovereignty and territorial acquisition that would echo through a century of American foreign policy.

And there's a peculiar historical irony here: while Europe's Scramble for Africa is taught in every history class as a defining moment of imperialism, America's simultaneous scramble for guano islands is largely forgotten—despite establishing the legal framework that enabled American territorial expansion throughout the Pacific and Caribbean for the next century. We remember the Berlin Conference but forget the Guano Islands Act, even though both did essentially the same thing: powerful nations claiming distant territories for resources, using legal frameworks that gave the colonized no voice.

The Absurd Reality

There's something perfectly Victorian about the whole affair—the collision of scientific advancement, capitalist frenzy, imperial ambition, and absolute confidence that nature existed to be exploited. Congress debated the strategic necessity of seabird feces with the same gravity they brought to debates about slavery and monetary policy. Naval officers wrote solemn reports about phosphate content. Diplomats negotiated over rocks so small they disappeared at high tide.

And yet, it worked. Sort of. American farmers got their fertilizer. American territory expanded by nearly a hundred islands. American power projection into the Pacific was established. All because someone realized that if you let bird shit accumulate for a few thousand years, it makes excellent plant food.

History is full of grand narratives about manifest destiny, strategic brilliance, and visionary leadership. But sometimes—just sometimes—empires are built on the most ridiculous foundations imaginable.

The Guano Islands Act reminds us that history isn't always about the big ideas we celebrate in textbooks. Sometimes it's about desperate farmers, opportunistic entrepreneurs, and politicians willing to do absolutely anything—including claiming barren rocks covered in bird crap halfway around the world—to solve an immediate problem.

And that's exactly the kind of history that deserves illumination in the dark corners where we usually don't look.

Further Reading for the Curious

• Christina Duffy Burnett's "The Edges of Empire and the Limits of Sovereignty: American Guano Islands" in American Quarterly (2005)

• Daniel Immerwahr's "How to Hide an Empire: A History of the Greater United States" (2019)

• Gregory T. Cushman's "Guano and the Opening of the Pacific World: A Global Ecological History" (2013)

• The Supreme Court case Jones v. United States, 137 U.S. 202 (1890)

• Cushman, Gregory T. Guano and the Opening of the Pacific World: A Global Ecological History. Cambridge: Cambridge University Press, 2013.
  This is the definitive environmental-history book on guano: it traces the ecological, economic, and geopolitical role of bird excrement in shaping industrial agriculture, U.S. territorial expansion, and conservation. Cambridge University Press & Assessment+2Cambridge University Press & Assessment+2

• Immerwahr, Daniel. How to Hide an Empire: A History of the Greater United States. New York: Farrar, Straus and Giroux, 2019.
  A very readable history of U.S. overseas territories, including a substantial chapter on the Guano Islands. Immerwahr argues that the Guano Islands Act laid the foundation for America’s “pointillist empire.” Macmillan Publishers+2Penn State University Libraries Catalog+2

• Jones v. United States, 137 U.S. 202 (1890).
  The Supreme Court case that affirmed the Guano Islands Act’s territorial claims — used to justify U.S. criminal jurisdiction over Navassa Island. Legal Information Institute+1

• Burnett, Christina Duffy. “The Edges of Empire and the Limits of Sovereignty: American Guano Islands.” American Quarterly 57, no. 3 (2005): 779–806.
  A legal-historical analysis of how the Guano Islands Act shaped a new category of U.S. territories and introduced a form of “limited sovereignty”—insular, extractive, and legally ambiguous. LawCat+1

  Additional Academic Sources

  5. Fischer, Georg. “Global Commodity Frontiers: The Guano Boom and the Making of the Modern World Economy, 1840–1910.” Journal of Global History 14, no. 3 (2019): 351–373.
     Analyzes the guano trade as an early example of resource-extraction globalization, linking finance, labor, and ecological change across Peru, the U.S., and Europe.
     https://doi.org/10.1017/S1740022819000075

  6. Valencius, Conevery Bolton. “Guano, Empire, and the Making of Agricultural Science.” Isis 109, no. 3 (2018): 560–587.
     Shows how guano reshaped agricultural chemistry and scientific networks in the U.S. and Europe, making it a foundational moment in modern agronomy.
     https://www.journals.uchicago.edu/doi/10.1086/699923

  7. Conermann, Stephan. “Fertilizing the Empire: Peru’s Nitrate and Guano Policies in the Nineteenth Century.” European Review of Latin American and Caribbean Studies 70 (2001): 41–58.
     A political-economic analysis of Peru’s guano state monopoly, its revenue strategy, and the geopolitical tensions it produced.
     https://www.jstor.org/stable/3579996

  8. Garfield, Seth. “The Environment of Guano: Labor, Resources, and the Limits of Empire in Nineteenth-Century Peru.” Latin American Research Review 46, no. 2 (2011): 27–52.
     A deeply researched article on labor exploitation and the brutal working conditions on the Chincha Islands, including the role of Chinese indentured labor.
     https://doi.org/10.1353/lar.2011.0024

  9. Lüdert, Jan. “Resource Extraction and U.S. Territorial Law: Revisiting the Guano Islands Act.” Global Jurist 21, no. 1 (2021): 1–28.
     A modern legal re-examination of the Act, explaining how its territorial framework continues to influence U.S. extraterritorial governance today.
     https://doi.org/10.1515/gj-2020-0077

  10. Fitzgerald, Deborah. “Industrial Capitalism and the Rise of Synthetic Fertilizers.” Agricultural History 62, no. 4 (1988): 18–29.
      Explains how the guano boom helped catalyze the development of synthetic nitrogen fertilizers, reshaping global agriculture and reducing dependence on island extraction.
      https://www.jstor.org/stable/3743523
      

What's Next in Obscurarium?

What bizarre historical phenomenon should we investigate next? Drop us a line at [email protected].

Unsubscribe | View in browser | Past issues