Kingman Reef is a largely submerged uninhabited tropical atoll located in the North Pacific Ocean, roughly half way between the Hawaiian Islands and American Samoa at . It is the northernmost of the Northern Line Islands and lies NNW of the next closest island (Palmyra Atoll), and about south of Honolulu.
The reef partly encloses a lagoon up to 73 meters deep, with the greater depths in the western part. At times, its shoreline might reach three kilometers in circumference; the total area within the outer rim of the reef is 76 km². There is just one small strip of dry land on the eastern rim, with an area of less than 0.01 km². The highest point on the reef is about one meter above sea level and wetted or awash most of the time, making Kingman Reef a maritime hazard. It has no natural resources, is uninhabited, and supports no economic activity.
The pre-20th century names Danger Reef, Caldew Reef, Maria Shoal and Crane Shoal refer to this atoll, which by then was still entirely submerged at high tide. Thomas Hale Streets described its state in the 1870s, when it had
"... hardly, as yet, assumed the distinctive features of an island. It is entirely under water at high tide, and but a few coral heads project here and there above the surface at low water. In the course of time, however, it will undoubtedly be added to the [northern Line Islands].
"Be it known to all people: That on the tenth of May, A.D. 1922, the undersigned agent of the Island of Palmyra Copra Co., Ltd., landed from the motorship Palmyra doth, on this tenth day of May, A.D. 1922, take formal possession of this island, called Kingman Reef, situated in longitude 162 degrees 18' west and 6 degrees 23' north, on behalf of the United States of America and claim the same for said company."
The lagoon was used in 1937 and 1938 as a halfway station between Hawai'i and American Samoa by Pan American Airways flying boats. In 1937, Pan Am had plans to anchor the ship North Wind as a floating tanker at Kingman and use the reef as a stopover for its flying boats on the route to New Zealand. It served as the base for the Sikorsky Clipper and the Samoan Clipper, captained by Edwin C. Musick, who made five successful landings in the lagoon in 1937 and 1938. The idea was abandoned as Pan Am found that the costs of supporting a mostly idle tanker ship prohibitive. There were also concerns that comfortable overnight accommodations would not be available in the event of a mechanical breakdown. As a result, Pan Am switched to Canton Island on May 18, 1939 and began services to New Zealand on July 12, 1940.