In 1935 personnel from the United States Navy's Patrol Wing Two carried out some minor construction to develop the atoll for seaplane operations.

[2] In November 1939 further work by civilian contractors commenced on Sand Island to allow the operation of one squadron of patrol planes with seaplane tender support.

On Sand Island, barracks for 400 men, a mess hall, an underground hospital, a radio station, water tanks, and a 100-foot (30 m) steel control tower were built.

[2]: 159 In July 1942 the civilian contractors at the atoll were replaced by 500 Seebees from the 5th and 10th Naval Construction Battalions, who expanded the fuel storage and water production at the base and built additional facilities.

[2]: 159  In December 1943 the 99th Naval Construction Battalion arrived at the atoll and proceeded to lengthen the runway to 6,000 feet (1,829 m) and add an additional 10 acres (4.0 ha) of parking to the seaplane base.