The reason that the United States has control of so many random islands has much to do with an odd law passed just a few years before the Civil War.
The United States is no exception, with its array of minor outlying islands, mostly in the Pacific Ocean. But there’s something weird about how many of these islands, mostly uninhabited today or used as minor scientific or military outposts, came under ownership of the United States.
See, in 1856, President Franklin Pierce signed a piece of legislation into law which may rank up there as the most unusual. The Guano Islands Act, which still exists today in the U.S. Code, basically makes it legal for U.S. citizens to claim unoccupied land in the name of the United States … if there’s a guano deposit on it.
(Thank you, President Pierce.)
Why was guano—or as most people call it, bird or bat poop—such a big deal? To put it simply, it was a hugely useful form of fertilizer in the days before those ingredients were available commercially. As Smithsonian magazine notes, the law directly resulted from the fact that significant guano discoveries were being made by American citizens … and there was no legal framework for what would happen next.
Understandably, the Pacific Commercial Advertiser, a newspaper originally distributed around whaling ports in Honolulu, frequently wrote about guano in the late 1850s. (It actually exists today, after a few mergers, as the Honolulu Star-Advertiser.)
In one 1858 piece, the newspaper repudiated claims by Commodore William Mervine and Commander Charles H Davis of the St. Mary’s ship, who had been called to islands in the Pacific to get a grasp of the quality of the guano. They said it wasn’t any good, but the guano shipments making it to the mainland United States suggested otherwise.
The Advertiser repudiated the comments in the article, citing a report on the guano quality from the Washington Era:
On the receipt of four tons of this guano in New York, by way of Panama, it was placed in possession of the Agricultural Bureau of the Patent Office, and has been distributed in bags of four pounds each to scientific agriculturists of the United States, and we are told the results are everywhere alike satisfactory, for, though out so rich in ammonia as the Peruvian guano, it contains more than seventy-five per cent. of phosphates of lime, for want of which cereal crops cannot be grown. This guano has been analyzed by the most eminent analytic chemists, for the Company and for the State of Maryland, and the superiority of the American Pacific island guano over the Peruvian is unquestionable.
Needless to say, the Advertiser was ready with a sick burn. “If the statements already made in this paper are correct, and they remain yet to be disproved, it will not be twelve months before the American public will condemn the acts and reports of Com. Marvin and Captain Davis, as a disgrace to the American Navy.”
Guano was a big deal in the 1850s, and no well-decorated U.S. Naval Officer was gonna stand in the way of the bird poop trade.