U.S. Marine Corps. Via ibiblio.org
Johnston Island (169.53W
16.73N) is little more than a large sand bar in an otherwise empty
ocean, 720 miles (1160 km) southwest of Pearl Harbor.
It is the only significant island in an atoll
9.3 miles (15 km) long and 2.5 miles (4 km) wide. The island itself
originally measured 1000 by 200 yards (900 by 180 meters) for an area
of only 64 acres (24 hectares) but was substantially enlarged through coral dredging during the war and
after. The island is nearly flat with little vegetation and is
surrounded by shallow water with numerous coral heads except to its
south. Rainfall averages 24 inches (61 cm) a year and
temperatures stay within the range of 70-80 F (20-30 C) year round.
The atoll has a large underwater shelf to leeward
that can anchor large numbers
vessels, but there is
no meaningful protection from storms
Nevertheless, some facilities were constructed, beginning in 1934. A
ship channel was dredged into the lagoon and the dredgings used to
create an artificial island, 300 by 800 feet (90 by 240 meters) to the
northeast of Johnston. This was used as a seaplane parking area. Three
seaplane lanes were also dredged. In September 1941 the island was
enlarged by filling in a 200 by 2500 foot (60 by 760 meter) on its
south shore, which made the island large enough for a 4000 foot (1200
When war broke out, Johnston was garrisoned by a
small detachment of 1
Battalion (162 men) with two 5" coastal guns
and four 3"
antiaircraft guns. A Seabee detachment arrived in July
1942 and dredged additional seaplane runways, using the dredgings to
expand the island again to make room for a second 3500 foot (1100
meter) runway. By 1944 the main runway had been expanded to 6000 feet
(1800 meters) and the island had grown to 160 acres (65 hectares).
Postwar the island was used for nuclear testing and storage of chemical
weapons, for which its location distant from any inhabited island or
sea lane but within reasonable travel distance from Hawaii made it ideal. It eventually
reached a size of 625 acres (255 hectares) through continued dredging.
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