Johnston Island is a low sand and coral island, 717 miles West-South-West of Honolulu. It is roughly a mile and a half long by a half mile wide, and reaches a greatest height of 44 feet in "Summit Peak" near its eastern end.

A mile and a half to the northeast of the main island is a small pile of sand and coral reef known as Sand or Agnes Island, about 200 yards in diameter and 8 feet high. Both islands are enclosed by a semicircular reef, 7.1/2 miles across, nearly continuous on the north, but open to the south. Much of the water within this semicircle is only 2 or 3 feet deep.

These islands are among the smallest, and certainly the most barren of all those which will be discussed. The vegetation consists of but three species of low herbs: Lepturus bunch grass, dry and brown over most of the surface, with scattered patches of Tribulus and Boerhaavia, both sprawling herbs.

The American brig Sally, of Boston, commanded by Joseph Pierpoint, grounded on a shoal near Johnston Island September 2, 1796, but gave no name to the land. 

H.B.M.S. Cornwallis is credited with its discovery, December 14, 1807, the name of her commanding officer, Captain Charles J. Johnston, being given the larger island.

On March 19, 1858, the captain of the American schooner Palestine took possession of the islands in the name of the United States. Three months later, June 14 to 19, 1858, the Hawaiian schooner Kalama, Captain Watson, with Samuel C. Allen on board, visited Johnston, removed the American flag, and hoisted that of Hawaii. The larger island was renamed Kalama Island, and the nearby smaller island was called Cornwallis.

Returning on July 27, 1858, the Captain of the Palestine again hoisted the American flag and reasserted the rights of the United States. This time he left two of his crew on the island to gather phosphate.

On July 27, 1858, and while these two men were still on the island, a proclamation of  Kamehameha IV declared the annexation of this island to Hawaii stating that it was "derelict and abandoned."

Following this eventful year, the history of Johnston Island became very quiet until quite recently. An occasional vessel stopped, but generally one look was enough. The U.S.S. Fenimore Cooper, under command of Lieutenant J. M. Brooks, paid a visit in 1859. The Nettie Merrill, under Captain Cluney, sailed to the Island from Honolulu, June 1, 1868, to investigate the guano deposits, returning on June 24. Occasionally, other vessels stopped to load guano.

In 1892, H.B.M.S. Champion made a survey and map, hoping that it might be suitable as a cable station. On January 16, 1893, the Hawaiian Legation at London reported a diplomatic conference over this temporary occupation of the island.

When Hawaii became an integral part of the United States in 1898, the name of Johnston Island was omitted from the list of Hawaiian Islands, but this did not keep the Territory from making use of it.

On September 11, 1909, Johnston was leased by the Territory of Hawaii to a private citizen for fifteen years. A board shed was built on the southeast side of the larger island, and a small tramline run up onto the slope of the low hill, to facilitate the removal of guano. Apparently neither the quantity nor the quality of the guano was sufficient to pay for gathering it, and although fish were abundant, the distance to market was too great, so that the project was soon abandoned. 

A survey was carried out by a scientific party, representing the U.S. Biological Survey and B. P. Bishop Museum, which visited Johnston Island July 10 to 20, 1923, on the U.S.S. Whippoorwill and U.S.S.  Tanager. In the party were also Commander John Rodgers (famous for his seaplane flight from California to Hawaii) and two other aviators, who made a pioneer flight over Johnston photographing it from the air.

Tents were pitched on the southwest beach of fine white sand, and a rather thorough biological survey was made of the island. Hundreds of sea birds, of a dozen kinds, were the principal inhabitants, together with lizards, insects, and hermit crabs. The reefs and shallow water abounded with fish and other marine life.

The maps here presented are drawn from the survey made at that time. The shore is alternately white sand and rough, jagged coral reef, as indicated.

By Executive Order, June 29, 1926, President Calvin Coolidge placed Johnston Island under the Department of Agriculture as a "refuge and breeding ground for native birds."

But the Department of Agriculture had no ships, and the Navy was also interested for strategic reasons, so another Executive Order, December 29, 1934, by President Franklin D. Roosevelt, placed the islands under the "control and jurisdiction of the Secretary of the Navy for administrative purposes," but subject to use as a refuge and breeding ground for native birds, under the Department of Agriculture. The 14th Naval District, Pearl Harbor, has immediate charge.

Several seaplanes have made flights from Hawaii to Johnston, such as that of a squadron of six planes in November, 1935. One of the most spectacular of these was on April 8, 1937, when two VP-6's made the round trip in ten and a half hours, to bring back a sick seaman.

During the two decades of the 1950s and the 1960s, the United States Air Force conducted a dozen nuclear-test launchings. Two of these missiles exploded directly over the runway on Johnston Island. Since then, the United States Government has spent four decades gathering the 60,000 cubic yards of radioactive contaminants that the aborted tests sprayed over Johnston Island.

In 1971 the United States Army started to stockpile 6.6 per cent of its chemical weapons on Johnston Atoll, moving them from Okinawa under operation Red Hat. The U.S. Army's 267th Chemical Company became responsible for the Islands stockpile of chemical weapons. During this period, both Air Force and Army tours of duty were considered an "unaccompanied" or "hardship" tour as no women or children were allowed on the Island. In 1985 the United States Congress ordered the disposal of all stockpiled chemical agents and munitions and construction began on the incineration plant. Destruction of the weapons began in 1990. In November 2000 the destruction operation was completed and involved more than 400,000 rockets, projectiles, bombs, mortars and mines. In April 2001 the United States Army Chemical Pacific closed and the clean-up of Johnston Island began.