Little is clearly understood about the prehistory of the Marshall Islands.
That successive waves of migratory peoples from Southeast Asia
spread across the Western Pacific about 3,000 years ago and that some
of them landed on and remained on these islands is about all that
researchers agree upon. The Spanish explorer Alvarode Saavendra
landed there in 1529. The islands were claimed by Spain in 1874. They
were named for English explorer John Marshall, who visited them in
1799.

Germany established a protectorate in 1885 and set up trading stations
on the islands of Jaluit and Ebon to carry out the flourishing copra
(dried coconut meat) trade. Marshallese Iroij (high chiefs) continued to
rule under indirect colonial German administration.

At the beginning of World War I, Japan assumed control of the
Marshall Islands. Their headquarters remained at the German center of
administration, Jaluit. U.S. Marines and army troops took control from
the Japanese in early 1944, following intense fighting on Kwajalein
and Enewetak atolls. In 1947, the United States, as the occupying
power, entered into an agreement with the UN Security Council to
administer Micronesia, including the Marshall Islands, known as the
Trust Territory of the Pacific Islands.

On May 1, 1979, in recognition of the evolving political status of the
Marshall Islands, the United States recognized the constitution of the
Marshall Islands and the establishment of the Government of the
Republic of the Marshall Islands. The constitution incorporates both
American and British constitutional concepts.

source: U.S. State Department Background Notes 1996