Johnston Atoll

Johnston Atoll is an unincorporated territory of the United States, under the jurisdiction of the United States Air Force (USAF). The island is closed to public entry, and limited access for management needs is only granted by a letter of authorization from the USAF. A special use permit is also required from the United States Fish and Wildlife Service (USFWS) to access the island by boat or enter the waters surrounding the island, which are designated as a National Wildlife Refuge and part of the Pacific Islands Heritage Marine National Monument. The Johnston Atoll National Wildlife Refuge extends from the shore out to 12 nautical miles, continuing as part of the National Wildlife Refuge System out to 200 nautical miles. The Pacific Remote Islands Marine National Monument extends from the shore out to 200 nautical miles.

The isolated atoll has been under the control of the U.S. military since 1934. During that time, it was variously used as a naval refueling depot, an airbase, a testing site for nuclear and biological weapons, a secret missile base, and a site for the storage and disposal of chemical weapons and Agent Orange. Those activities left the area environmentally contaminated. The USAF completed remediating the contamination in 2004 and performs only periodic monitoring today.

The island is home to thriving communities of nesting seabirds and has significant marine biodiversity. USAF and USFWS teams conduct environmental monitoring and maintenance to protect the native wildlife. In the 21st century, one ecological problem was yellow crazy ants that were killing seabirds, but by the 2020s these were eradicated.

The atoll originally consisted of two islands, Johnston and Sand island surrounded partially by a coral reef. Over the 20th century, those two islands were expanded, and two new islands, North (Akau) and East (Hikina) were created mostly by coral dredging. A long airstrip was built on Johnston, and there are also various channels through the coral reef.