'Rare minerals' - 1856 vs 2025

There’s much talk right now about a U.S. interest in 'buying' Greenland. Though with its own government since 1979, Greenland is a part of the Kingdom of Denmark (which also includes the Faroe Islands).

The interest is primarily for the geography - the US already has a military base on main Greenland and both NATO and Russia have ramped up military bases in the Artic in the past decade. Another motivation is the presence of oil and rare earth mineral deposits in the region.

Apparently the US has acquired islands for minerals (of a slightly different nature) before. In 1856, the U.S. Congress passed the Guano Islands Act that

allowed any U.S. citizen to lay claim to any deserted guano island anywhere in the world and make it U.S. territory. The law essentially deputized all Americans to claim land in their nation’s name.

Guano were literal mountains created over centuries from the droppings of seabirds, and became especially prized in the 17-1800s for the use of crushed rock from these as fertilizer. They contained nitrogen and potassium in high concentration and were easily the best farm yield-boosters humanity had ever known.

As per Thomas Hager’s The Alchemy of Air (very interesting), the US ended up with a total of ‘ninety four islands, rocks and keys’ as a result of the 1856 Act. Most of these did not have much guano, and ended up serving other purposes - as airstrips and staging areas during WWII and even as a CIA base.