In 1899, Hawaii was officially annexed into the union. That same year, the United States established a military base on the island. Pearl Harbor was later expanded to accommodate more naval ships. In May of that year, Commander John F. Murray was appointed naval representative with authority to conduct business for the Naval Department and its Bureaus. Upon appointment, Murray immediately assumed control of the Coal Depot. To support his facilities, he was assigned the tugboat USS Iroquois and two coal barges. This all led to the establishment of “Naval Station, Honolulu” in mid-November of 1899. However, on February 2nd, 1900, the name would be changed to “Naval Station, Hawaii.” Its creation allowed the Navy to explore territorial outposts.
From 1900 to 1908, the Navy devoted time and resources to further improving the base. Thanks to the passing of the Appropriation Act in 1901, additional sheds and housing were built on the naval reservation. This also included a machine shop, smithery and foundry, commandant’s house and stables, cottage for the watchman, fencing, 10-ton wharf crane, and water pipe system. Pearl Harbor was later dredged, and the channel was made larger for the accommodation of bigger ships.
Thanks to the Appropriations Act, Congress approved the acquisition of more land to develop the naval station at Pearl Harbor further and improve the channel to the Lochs. Under the direction of the Bureau of Equipment, the Commandant attempted to acquire options for lands surrounding Pearl Harbor that were recommended for naval activity. However, negotiations failed because they were unable to agree on a purchase price with the landowners.
Undeterred, on July 6th, 1901, the United States government used eminent domain to acquire the land. The land acquired in this suit included the present-day Naval Yard, Kauhua Island, and parts of the southeast coast of Ford Island. This would be a part of the United States' broader plan to increase its naval presence in the Pacific. A year later, U.S. engineers began digging a channel in Pearl Harbor, turning it into the world’s leading Naval base. The drilling of the coral reef blocking Pearl Harbor progressed so well that by January of 1905, the gunboat Petrel was able to move to the upper part of Main Loch.
As the naval station grew, one of the concerns was the army’s intention to make claims on the base’s property. Due to their facilities and the access to wharves, cranes, artesisan wells, and coal supplies, the Army made several requests to use the station for their own activities. In February 1901, the Army applied to use the Naval docks' movable cranes for handling coal and other material, a saluting battery, a flag staff on the reservation, and the exclusive use of an artesisan well. However, the Bureau of Equipment denied all their requests due to concerns that the army would permanently take over the property and potentially exclude the Navy. The Bureau of Equipment’s warning was proven correct when, in 1902, the Depot Quartermaster said that the goodwill of the Army provided any water from the artesian well.
However, despite the warnings of the Bureau of Equipment, three different government departments secured permission to settle on the reservation. This included the War Department, the Department of Labor and Commerce, and the Department of Agriculture. In 1903, the Department of Labor and Commerce received seven acres of land to establish an Immigration Station. The Department of Agriculture secured part of the site originally intended for a hospital to be used as an experimental station.
By 1906, the Commandant believed that the Bureau of Yards and Docks should develop more policy on the future of the station. The docks had been mostly used by Army transports instead of Navy ships. Meanwhile, the Army was also trying to gain control of the Quarantine Wharf. The wharf had been built previously by the Territorial Government on the reservation. However, there was an understanding that the Navy could take it at any time, provided they paid for it at appraised value. However, the Commandant was against the activities of the other departments. It believed that if the station was going to develop beyond a coal depot, the other activities had to end, particularly when they were enjoying the benefits of naval establishments. The Commandant even went as far as to encourage the Navy to increase improvement activities on the Naval Station.
In 1908, the Pearl Harbor Naval Yard was officially established. The Naval Station saw its greatest growth from 1908 to 1919. Congress passed the Act of 13 May 1908, which authorized the enlargement and dredging of the Pearl Harbor channel and lochs to accommodate the largest ships. The act also allowed for the building of shops, supply houses, and a drydock. Work on the dock began in September 1909. However, despite much wrangling with Congress to secure three million dollars for its construction, the dock collapsed in 1913 due to “underground pressure.” In 1917, Ford Island was purchased for joint use by the Army and Navy in the development of military aviation in the Pacific.
In April 1901, the harbor achieved a milestone when the barquentine Amaranth became the fourth deep-sea, cargo-carrying vessel to move through the newly dredged harbor. This accomplishment was preceded by the three-masted schooner W.H. Marston on March 8th, and the schooner Ariel and bark Marston just a few days later.
Due to the Imperial Japanese Military continuing to wage war in China, there was a growing concern over Japan’s intentions. In response, starting in February 1932, led by Rear Admiral Thomas Yarnell, the Navy conducted a mock attack on Pearl Harbor known as Fleet Problem 13, using aircraft carriers to launch a surprise aerial attack. To many observers, the exercise was an overwhelming success, and it showed the vulnerabilities of the base to air attacks, particularly their ability to destroy airfields and ships. However, the findings were ultimately dismissed by Admirals William S. Pye and Husband E. Kimmel, viewing them as unrealistic and merely theoretical. This left the Navy unprepared for Japan’s impending attack