El Yunque

Its protection goes back to 1876, when King Alfonso XII of Spain declared 5,000 hectares of the Sierra de Luquillo a Crown forest reserve, making it one of the oldest legally protected forest reserves in the whole western hemisphere, barely four years younger than Yellowstone. After Puerto Rico was ceded to the United States in 1898, President Theodore Roosevelt established the Luquillo Forest Reserve in 1903 over the former Spanish Crown lands, and in 2007 the forest officially recovered its traditional Taíno name, El Yunque. It is the only tropical rainforest in the entire United States National Forest System, and is home to the Puerto Rican parrot, one of the most threatened birds on the planet, whose wild population fell to barely 13 birds in the 1970s before a captive breeding programme allowed a partial recovery.