In the mid-nineteenth century, explorers headed out to sea, hoping to claim new islands for the United States. One seemed promising: “These islands are small, high and rocky, barren and uninviting to the last degree, yet out of them has come wealth to stagger the dreams of oriental imagination.”  These islands held an extremely valuable resource. With high levels of both phosphorus and nitrogen, it was excellent for crops. In his 1850 State of the Union, President Millard Fillmore said this resource had “become so desirable an article to the agricultural interest of the United States that it is the duty of the Government to employ all the means properly in its power for the purpose of causing that article to be imported into the country at a reasonable price.”  This article would enable American farmers to produce on a larger scale, at a time when farming was undergoing vast changes as a result of the Industrial Revolution. This prized new resource was guano.

That’s right. American explorers were looking for islands filled with bird poop. They were not the first to think of using guano as a fertilizer. Guano had been harvested and used for centuries. In fact, the word “guano” comes from the Quichua language of the Inca Empire. It is most commonly found in islands in the Caribbean. The conditions in the islands near present-day Peru were perfect for forming large deposits of guano. A large sea bird population meant there was plenty of excrement settling on the ground. What really made the islands perfect, however, was the extreme dry heat. This enabled the guano to dry out and solidify—making it perfect for harvesting. For the Incans, guano was a highly prized fertilizer. Disturbing sea birds (and thereby disrupting the process of making guano) was punishable by death.

“The Great Guano Deposits of Peru,” Bulletin of the International Union of the American Republics, (Washington: Government Printing Office, 1909), 884.
“The Great Guano Deposits of Peru,” Bulletin of the International Union of the American Republics, (Washington: Government Printing Office, 1909), 884.

When the Spanish first arrived in the Inca Empire in the 1500’s, they were aware that people used guano as fertilizer for their crops. As the Perrysburg Journal noted in 1855, “the Spaniards obtained this knowledge from them [the Inca], but were too indolent to apply it in practical life.”  Europeans and North Americans remained unfamiliar with the benefits of guano until the nineteenth century. From 1799 to 1804, Prussian explorer Alexander von Humboldt traveled around Latin America. In 1802, while in Peru, he investigated the fertilizing properties of guano. After hearing how effective it was, guano soon became highly prized on the world market. In 1840, the first Peruvian guano was shipped to Europe, arriving in London. Over the next two years, 182 tons were shipped to England. Just twenty years later, in 1862, that amount had risen to 435,000 tons.


By the 1850’s, news of this revolutionary fertilizer being imported by the British had reached the United States. Americans wanted a piece of the lucrative industry. One writer said, “The commercial enterprise of our country is seeking out and bringing the treasures of the waters to our farms and orchards, in the form of guano…Treasures, indeed—rich in the one needful thing, without which our labor would be in vain, our fertile soils a barren waste.”

The American Guano Company formed in New York City in September of 1855. The company already had an island in mind that they wished to mine. They reported that “excepting this one, no Guano Island hitherto discovered possesses the natural advantages of a good harbor, safe anchorage, and convenience to load a large number of ships at once.” “From the past and present demand for Peruvian guano, now selling at fifty-five dollars per ton,” the company estimated that their profits would be $2,400,000 per annum.

American companies had seen the success associated with the guano industry and were eager to get involved. Congress facilitated this in an interesting way by enacting the “Guano Islands Act” on August 18, 1856. This new law allowed U.S. citizens to claim islands containing guano deposits for the United States:

That when any citizen or citizens of the United States may have discovered, or shall hereafter discover, a deposit of guano on any island, rock, or key not within the lawful jurisdiction of any other government, and not occupied by the citizens of any other government, and shall take peaceable possession thereof, and occupy the same, said island, rock, or key may, at the discretion of the President of the United States, be considered as appertaining to the United States.

The law further specified that when guano on any given island ran out, the United States would have no obligation to retain the territory:

“And be it further enacted, that nothing in this act contained shall be construed obligatory on the United States to retain possession of the islands, rocks, or keys, as aforesaid, after the guano shall have been removed from the same.”

The Guano Islands Act marked the beginning of insular, unincorporated territories of the United States. According to the U.S. Office of Insular Affairs, an insular territory is “a jurisdiction that is neither a part of one of the several States nor a Federal district.”  Thus far, territory acquired by the United States as part of westward expansion was intended for eventual statehood. The guano islands were not meant to be populated by Americans or entered into the union of the United States. The explicit purpose of holding the islands was to mine guano, an increasingly valuable resource for the United States.

Baker Island was the first island to become a part of the United States under the Guano Islands Act. Although it was first discovered by whalers in 1818, the U.S. took possession of it in 1857.


The acquisition of territory through the Guano Islands Act seemed relatively straightforward. However, this was the first time the United States attempted to annex overseas territories.

Although the Guano Islands Act specifically indicated that American explorers could only claim “any island, rock, or key not within the lawful jurisdiction of any other government, and not occupied by the citizens of any other government,” this did not prevent territorial disputes. In 1857 Peter Duncan and Edward Cooper of Maryland discovered that Navassa Island off the coast of Haiti held 1,000,000 tons of guano. The Haitian government felt that Navassa Island was definitely “within the lawful jurisdiction” of the Haitian government.

Regardless of Haiti’s claim, Duncan and Cooper claimed it for the United States under the Guano Islands Act. President James Buchanan approved the annexation.

In 1918 the Ogden Standard said that Navassa Island had “long since proved to be the most troublesome, to the square mile, of any property this nation even came into possession of.” The Americans, led by Edward Cooper and the newly formed Navassa Phosphate Company, immediately began mining guano once Navassa became a U.S. possession. The company brought in droves of slave labor, such that “the crack of the slavedriver’s whip was soon heard where only the scream of the seagull had broken the silence for centuries.”

Haiti had not, however, given up its right to the island. In November or 1858, Mr. B.C. Clark, the commercial agent of Haiti in Boston, wrote that since the Haitian government “never ceded, sold, or leased either of these dependencies [including Navassa] to any nation, company, or individual,” the island remained a Haitian possession. The U.S. Assistant Secretary of State replied that the annexation of Navassa by the United States was lawful since “the island was derelict and abandoned, with guano of good quality.”

The Haitian government “sent two vessels of war and soldiers to the island and interrupted and prohibited Cooper and his men digging or taking away any of the rock.”  The U.S. Secretary of State, Lewis Cass, issued a letter to the Secretary of the Navy, Isaac Toucey, which read:

“The president being of the opinion that any claim of the Haitian Government to prevent citizens of the United States from removing guano from the Island of Navassa is unfounded…directs that you will cause a competent force to repair to that island, and will order the officer in command thereof to protect citizens of the United States in removing guano therefrom against any interference from authorities of the Government of Haiti, or of any other government.”

The Secretary of the Navy relayed the President’s message to the Haitian minister of foreign relations. This stern message, along with the arrival of “one of Uncle Sam’s most vicious looking war vessels,” quieted the conflict enough for Americans to continue mining.

The question of jurisdiction was never entirely resolved. But, the matter did not hold much importance for the U.S. government so long as the Navassa Phosphate Company could continue mining.

The issue of jurisdiction became paramount when Henry Jones murdered Thomas N. Foster in 1889. In 1889, there were 137 black laborers and 11 white officers on Navassa. On September 14, “a riot took place there, in which a large number of laborers were engaged against the officers, and the defendant killed Thomas N. Foster, one of the officers, under circumstances which the jury found amounted to murder.”

The defendant, Jones, was brought to Maryland for his murder trial. The jury there found him guilty and he was sentenced to death. He appealed his case to the United States Supreme Court, claiming that the District Court of Maryland had no authority to try him for crimes committed in Navassa Island. Originally, acquiring overseas territory through the Guano Islands Act was a commercial endeavor. Now, the United States was faced with establishing rule of law in far-flung territories. In order to try Jones for murder in the American judicial system, the United States had to prove that “Navassa Island was recognized and considered by the United States as appertaining to the United States, and in the possession of the United States under the provisions of the laws of the United States.” 

In 1890, the United States Supreme Court found that “the Island of Navassa must be considered as appertaining to the United States; that the Circuit Court of the United States for the District of Maryland had jurisdiction to try this indictment, and that there is no error in the proceedings.” 


American companies mined huge guano deposits on a number of islands in the Caribbean and Pacific. But, the more companies mined, the less sea birds visited the islands to renew the resource. In the long run, guano was not beneficial as a fertilizer.

The Anderson Intelligencer, Feb 22, 1914.
The Anderson Intelligencer, Feb 22, 1914.


The Ogden Standard wrote:

“There was a time when guano was in unusual demand in the United States. Farmers had found their soil was enriched by its use. But because the science of using commercial fertilizer was then crude, guano finally fell into smaller use. After three of four years treatment with guano, land failed to yield to its influence and the farmers found that in the long run the ground would have been better off if it had not been used.”

Guano Mining, Navassa Island.
Guano Mining, Navassa Island.


Eventually, the guano industry fell by the wayside, but the islands remain significant in American history. The Guano Islands set a precedent for insular and unincorporated territory. According to the U.S. Office of Insular Affairs, an unincorporated territory is “a United States insular area in which the United States Congress has determined that only selected parts of the United States Constitution apply.”  The Guano Islands were the first overseas territories acquired by the United States. The issues the government faced with incorporating the Guano Islands were were revisited in 1898, when the United States acquired its first peopled territories—not for commercial reasons, but for colonization. Although Navassa was “only a wind-swept and wave-battered rock rising out of the Caribbean Sea,” it and other Guano Islands were the beginning of U.S. overseas territorial expansion.

For more information:

  1. “The Great Guano Deposits of Peru,” Bulletin of the International Union of the American Republics, Washington: Government Printing Office, 1909, 884
  2. “Millard Fillmore: 1850 State of the Union Address,” Presidential Rhetoric 
  3. “The Guano Isles, “ Perrysburg Journal, December 29 1855
  4. “The Great Guano Deposits of Peru,” Bulletin of the International Union of the American Republics, Washington: Government Printing Office, 1909, 888.
  5. Prospectus of the American Guano Company, New York: John F. Trow Printer, 1855, 8
  6. ibid., 4
  7. ibid., 5
  8. “Definitions of Insular Area Political Organizations,” Office of Insular Affairs
  9. “And It’s Only a Wind-Swept and Wave-Battered Rock Rising Out of the Caribbean Sea—Almost At War Over Guano Phosphate Deposits,” Ogden Standard, April 16, 1918
  10. ibid.
  11. “Freedom for a Slave,” Kansas City Journal, Feb 12, 1899
  12. Jones v. United States, 1890
  13. “And It’s Only a Wind-Swept and Wave-Battered Rock..”
  14. ibid.
  15. Jones v. United States, 1890
  16. ibid.
  17. ibid.
  18. “And It’s Only a Wind-Swept and Wave-Battered Rock…”
  19. “Definitions of Insular Political Organizations”
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