In the mid-19th century, global agriculture underwent a major revolution fueled by a surprising commodity: dried bird excrement, known as guano. Rich in nitrogen and phosphate, guano proved to be an extraordinary fertilizer that dramatically boosted agricultural yields across Europe and North America. As demand skyrocketed, a geopolitical scramble for guano-rich islands erupted.
To ensure American farmers secured a steady supply without paying exorbitant prices to foreign monopolies, the United States Congress passed the Guano Islands Act of 1856. This astonishing piece of federal legislation empowered any U. S.
citizen to take possession of an unclaimed, uninhabited island, rock, or key anywhere in the world, provided it contained guano deposits. Once claimed and occupied, the U. S.
President was authorized to deploy the armed forces to protect the citizen's claim, effectively making the island an unorganized territory of the United States. Over the following decades, American entrepreneurs claimed more than 100 islands, atolls, and reefs under this statute, ranging from the Caribbean to the deep Pacific Ocean. Notable territories acquired through bird poop include Midway Atoll, Baker Island, Howland Island, and Johnston Atoll—places that later played pivotal strategic roles during World War II and Cold War defense programs.
Remarkably, the Guano Islands Act remains active federal law today, meaning an enterprising American who finds an unclaimed, guano-covered island could still theoretically expand the sovereign domain of the United States.