definition of Wikipedia
Johnston Atoll is a 1.03 sq mi (2.7 km2) atoll in the North Pacific Ocean about 750 nmi (860 mi; 1,390 km) west of Hawaii. The atoll, which is located on the coral reef platform, comprises four islands. Johnston and Sand islands are both enlarged natural features, while North (Akau) and East (Hikina) are two artificial islands formed by coral dredging. Johnston Atoll is grouped as one of the United States Minor Outlying Islands.
For nearly 70 years, the atoll was under the control of the American military. In that time it was used as an airbase, a naval refuelling depot and a weapons testing area. In the mid 1980s, the atoll became a facility for Chemical weapons disposal. In 2004 the military base was closed; island control was handed over to civilian authorities.
Johnston is an unincorporated territory of the United States administered by the United States Fish and Wildlife Service of the Department of the Interior as part of the Pacific Remote Islands Marine National Monument.
The first European record of the atoll was on September 2, 1796 when the American brig Sally accidentally grounded on a shoal near the islands. The ship's captain, Joseph Pierpont, published his experience in several American newspaper the following year giving an accurate position of Johnston and Sand Island along with part of the reef. However he did not name or lay claim to the area. The islands were not officially named until Captain Charles J. Johnston of the Royal Naval ship HMS Cornwallis sighted them on December 14, 1807.
By 1858, Johnston Atoll was claimed by both the United States and the Kingdom of Hawaii. The islands came under the jurisdiction of the United States following the Reciprocity Treaty of 1875 with Hawaii. By 1890 the atoll's entire guano deposits had been depleted (mined out) by U.S. interests operating under the Guano Islands Act.
From July 10–22, 1923, the atoll was recorded in a pioneering aerial photograph project.
On December 29, 1934, President Franklin D. Roosevelt transferred control of Johnston Atoll to the United States Navy in order to establish an air station, and also to the Department of the Interior to administer the bird refuge. In 1936, the Navy began to develop a base for seaplanes and an airstrip with refueling facilities. On February 1941 Johnston Atoll was designated as a Naval Defensive Sea Area and Airspace Reservation.
The atoll was briefly shelled by Japanese naval units shortly after the attack on Pearl Harbor in December 1941. But as the Pacific War soon shifted west, the island's role changed from being a combat outpost to a refuelling and resupply base for American aircraft and submarines.
The Johnston Atoll area was used during the 1950s and 1960s as an American nuclear weapons test site—for both above-ground and underground nuclear tests. Later on, it became the site of a chemical weapons depot and the site of the Johnston Atoll Chemical Agent Disposal System (JACADS). All of the chemical weapons that were once stored on Johnston Island have been incinerated, and that process was completed in 2000 and JACADS demolished by 2003.
Between 1958 and 1975, several scientific sounding rockets were launched from Johnston Island. There were also several nuclear test missiles that were launched from Johnston Island in 1962 during the "Operation Dominic" series of nuclear tests, from a launchpad at . Twelve thermonuclear warheads were exploded in all, one of which was deliberately disrupted when the PGM-17 Thor carrying it failed to launch scattering plutonium debris over the island. Afterwards, the radioactive debris and soils were placed in a 25 acres (100,000 m2) landfill on the island, along with residue from Agent Orange containers returned from Southeast Asia after the Vietnam War, PCBs, PAHs, dioxins, and sarin nerve gas from the Soviet Union and East Germany.
In 1963, the U.S. Senate ratified the Limited Test Ban Treaty, which contained a provision known as "Safeguard C". Safeguard C was the basis for maintaining Johnston Atoll as a "ready to test" above-ground nuclear testing site should atmospheric nuclear testing ever be deemed to be necessary again. In 1993, Congress appropriated no funds for the Johnston Atoll "Safeguard C" mission, bringing it to an end. Congress redefined the island's military mission as the storage and destruction of chemical weapons.
It was used for rocket-launched nuclear tests in the 1950s. In the 1960s it was the site for the operational Program 437 anti-satellite system. Several sounding rockets were also launched over the years. Known to have been used for 124 launches from 1958 to 1975, reaching up to 1158 kilometers altitude.
In 2003, all structures and facilities, including those used in JACADS, were removed, and the runway was marked closed. The last flight out for official personnel was June 15th, 2004.  After this date, the base was completely deserted, with the only structure left standing being the JOC building at the east end of the runway.
On August 22, 2006, Johnston Island was struck by Hurricane Ioke. The eastern eye-wall passed directly over the atoll, with winds exceeding 100 mph (160 km/h). Twelve people were actually on the island when the hurricane struck, part of a contracted USAF crew sent to the island to monitor groundwater contamination levels. All 12 survived. 
On December 9, 2007, the United States Coast Guard swept the runway at Johnston Island of debris and used the runway in the removal and rescue of an ill Taiwanese fisherman to Oahu, Hawaii. The fisherman was transferred from the Taiwanese fishing vessel Sheng Yi Tsai No. 166 to the Coast Guard buoy tender Kukui on December 6, 2007. The fisherman was transported to the island, and then picked up by a Coast Guard HC-130 Hercules rescue plane from Kodiak, Alaska.
Since the base was closed, the atoll is likely to have been visited by sailing vessels crossing the Pacific, as the deserted atoll has a strong lure due to the activities once performed there. One vessel blogged about stopping there for several days during a trip from Honolulu to the Marshall Islands.
In 2010, a Fish and Wildlife survey team identified a swarm of Anoplolepis ants that had invaded the island. The crazy ants are particularly destructive to the native wildlife, and needed to be eradicated. A "Crazy Ant Strike Team" was formed to stay on the island for nine months to bait traps for the ants and eliminate them. The team camped in the old chemical weapons storage bunkers on the southwest corner of the island. It is believed that the ants arrived with private boaters visiting the island illegally.  
In 1926, Johnston Atoll was designated a federal bird refuge by President Calvin Coolidge with Executive Order 4467. The island was later converted to a National Wildlife Refuge and now includes 696 acres (2.82 km2) of land and over 800,000 acres (3,200 km2) of water area. While the outer islets and water rights are part administered by the Fish and Wildlife Service, the actual land mass remains under Navy control for cleanup purposes. Along with six other islands, the atoll was administered as part of the Pacific Remote Islands National Wildlife Refuge Complex. On January 6th 2009, that entity was upgraded to the Pacific Remote Islands Marine National Monument by President George W. Bush.
Johnston Atoll has never had any indigenous inhabitants, although during the late part of the 20th century, there were averages of about 300 American military personnel and 1,000 civilian contractors present at any given time.
The central means of transportation to this island was the airport, which had a paved military runway. The islands were wired with 13 outgoing and 10 incoming commercial telephone lines, a 60-channel submarine cable, 22 DSN circuits by satellite, an Autodin with standard remote terminal, a digital telephone switch, the Military Affiliated Radio System (MARS station), a UHF/VHF air-ground radio, and a link to the Pacific Consolidated Telecommunications Network (PCTN) satellite. Amateur radio operators occasionally transmitted from the island, using the KH3 callsign prefix.
Johnston Atoll's economic activity was limited to providing services to American military personnel and the contractors residing temporarily on the island. All foodstuffs and manufactured goods were imported. The base had six 2.5 megawatt (MW) electrical generators supplied by the base's support contractor, Holmes and Narver, using Enterprise Engine and Machinery Company DSR-36 diesel engines. The runway was also available to commercial airlines for emergency landings (a fairly common event), and for many years it was a regular stop on Continental Micronesia airline's "island hopper" service between Hawaii and the Marshall Islands.
There were no official license plates issued for use on Johnston Atoll. U.S. government vehicles were issued U.S. government license plates and private vehicles retained the plates from which they were registered. According to reputable license plate collectors, a number of "Johnston Atoll license plates" were created as souvenirs, and have even been sold on-line to collectors, but they were not officially issued.
The four islands compose a total land mass of 2.67 km². Due to the atoll's tilt, much of the reef on the southeast portion has subsided. But even though it does not have an encircling reef crest, the reef crest on the northwest portion of the atoll does provide for a shallow lagoon, with depths ranging from 3–10 m (9.8–33 ft).
|North (Akau) Island||-||10|
|East (Hikina) Island||-||7|
Its climate is tropical but generally dry. Northeast trade winds are consistent and there is little seasonal temperature variation. With elevation ranging from sea level to 5 m (16 ft) at Summit Peak, the islands contain some low-growing vegetation on mostly flat terrain and no natural fresh water resources.
About 300 species of fish have been recorded from the reefs and inshore waters of the atoll. It is also visited by Green Turtles and Hawaiian Monk Seals. Seabird species recorded as breeding on the atoll include Bulwer's Petrel, Wedge-tailed Shearwater, Christmas Shearwater, White-tailed Tropicbird, Red-tailed Tropicbird, Brown Booby, Red-footed Booby, Masked Booby, Great Frigatebird, Spectacled Tern, Sooty Tern, Brown Noddy, Black Noddy and White Tern. It is visited by migratory shorebirds, including the Pacific Golden Plover, Wandering Tattler, Bristle-thighed Curlew, Ruddy Turnstone and Sanderling.
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