The three posts were designed to prevent a hostile fleet from reaching such targets as the Puget Sound Naval Shipyard and the cities of Seattle, Tacoma and Everett.

To meet construction needs, the Army laid a pipeline from Port Townsend and pumped water into large storage tanks inside the fort.

The 126th Coast Artillery Company, consisting of 87 soldiers commanded by Captain Manus McCloskey, was the first detachment assigned to Fort Worden.

By the fall of 1905, Fort Worden was fully staffed with four Coast Artillery companies, and the harbor defense system, costing approximately $7.5 million, was considered complete and operational.

During World War I, the complement at Fort Worden was greatly expanded as soldiers arrived for training prior to being sent to European battlefields.

During World War II, Fort Worden remained the headquarters of the Harbor Defense Command and it was jointly operated by the Army and Navy.

The Army operated radar sites and coordinated Canadian and U.S. defense activities in the Strait of Juan de Fuca and Puget Sound.

The Navy, responsible for the detection and identification of all vessels entering and leaving Puget Sound, monitored new underwater sonar and sensing devices.

Fort Worden personnel also manned batteries and fire control towers at the Cape George Military Reservation, six miles (9.7 km) southwest of Port Townsend on the Strait of Juan de Fuca at the entrance to Discovery Bay.

It remained active as an administrative unit until June 30, 1953, when the Harbor Defense Command was deactivated and the fort officially closed, ending fifty-one years of military jurisdiction.

At the outset of the Korean War, the 2nd Engineer Special Brigade was among the first Army units ordered to Korea to reinforce the Far East Command.

[20] The park also is the home of the Port Townsend Marine Science Center, whose natural history museum, hands-on tidepool exhibits and educational programs promote understanding about coastal ecosystems.

Goddard College's Port Townsend campus hosts several of its program residencies at Fort Worden in the former base hospital building.

One notable feature of the park is the 2,000,000 gallon underground cistern, originally built to hold water for fire-fighting in the event that the fort was attacked and put to the torch.

This huge subterranean chamber has an acoustical reverberation time of around 45 seconds, and once attracted the interest of various musicians and recording artists, among them Wayne Horvitz, Pauline Oliveros, and Stuart Dempster.

A small military cemetery, maintained by the Public Works Directorate at Joint Base Lewis-McChord, is located at the south side of the state park.