Guano Islands Act

The Guano Islands Act (, enacted August 18, 1856, codified at §§ 1411-1419) is a United States federal law passed by the U.S. Congress that enables citizens of the United States to take possession, in the name of the United States, of unclaimed islands containing guano deposits. The islands can be located anywhere, so long as they are not occupied and not within the jurisdiction of another government. It also empowers the President of the United States to use the military to protect such interests and establishes the criminal jurisdiction of the United States in these territories.
Background.
In the 1840s, guano came to be prized as a source of saltpeter for gunpowder as well as an agricultural fertilizer. 
The United States began importing it in 1843 through New York. By the early 1850s, the U.K. imported over 200,000 tons a year, and U.S. imports totaled about 760,000 tons. The "guano mania" of the 1850s led to high prices in an oligopolistic market, attempts of price control, fear of resource exhaustion, and eventually the enactment of the "Guano Islands Act 1856" in August 1856. The Act enables U.S. citizens to take possession of unclaimed islands containing guano for the U.S., and empowered the President to send in armed military to intervene. This encouraged American entrepreneurs to search and exploit new deposits on tiny islands and reefs in the Caribbean and in the Pacific.
This was the beginning of the concept of insular areas in U.S. territories. Up to this time, any territory acquired by the U.S. was considered to have become an integral part of the country unless changed by treaty and eventually to have the opportunity to become a state of the Union. With insular areas, land could be held by the federal government without the prospect of its ever becoming a state in the Union.
Under the act the US gained control of around 94 islands. By 1903, 66 of these islands were recognized as territories of the US.
Criminal jurisdiction.
Section 6 provides that criminal acts on or adjacent to these territories "shall be deemed committed on the high seas, on board a merchant ship or vessel belonging to the United States; and shall be punished according to the laws of the United States relating to such ships or vessels and offenses on the high seas ..." The provision was considered and ruled constitutional by the U.S. Supreme Court in "Jones v. United States", .
Result.
The Act continues to be part of the law of the United States. The most recent Guano Islands Act claim was made to Navassa Island. However, the claim was denied because an American court ruled the island was already under American jurisdiction (a claim Haiti disputes).
Claims.
More than 100 islands have been claimed for the United States under the Guano Islands Act, but most claims have been withdrawn. The Act specifically allows the islands to be considered possessions of the U.S. The Act does not specify what the status of the territory is after it is abandoned by private U.S. interests or the guano is exhausted, creating neither obligation to nor prohibition of retaining possession.
The islands still claimed by the United States under the Act are:
Disputed claims.
A few islands claimed by the United States under the "Guano Act of 1856" are disputed. 