Honouliuli was the largest and longest-used civilian internment camp in Hawaiʻi during the Second World War. After the attack on Pearl Harbor, martial law and wartime suspicion led authorities to arrest people—many of Japanese ancestry—without ordinary due process. The U.S. Army opened the camp in March 1943 in a secluded gulch on Oʻahu, transferring internees from Sand Island and other locations. Sugarcane fields and steep slopes hid the compound from public view and intensified the isolation of those confined there.

The roughly 160-acre installation contained seven compounds, barracks, tents, fences, guard towers, administrative buildings, kitchens, latrines, and medical facilities. Barbed wire separated civilians from prisoners of war and divided people by status, nationality, and gender. Over its operation, approximately 400 civilian internees and about 4,000 prisoners of war passed through Honouliuli. The POW population included Japanese, Okinawan, Korean, Italian, and other captives. Japanese American internees called the hot, damp gulch Jigoku-Dani, or “Hell Valley.”

Civilian detainees included Buddhist priests, language-school teachers, journalists, businesspeople, and community leaders whom authorities regarded as influential or suspicious. Many were U.S. citizens or long-term Hawaiʻi residents, and evidence of individual wrongdoing was often absent. Families endured separation, stigma, lost income, and uncertainty while navigating military hearings and transfers. Internees organized art, worship, gardening, sports, and mutual aid within confinement. Their experiences differed from the mass removal on the continental West Coast, but arose from the same racial prejudice and expansion of wartime executive power.

Honouliuli closed in 1946. Buildings were removed, vegetation reclaimed the gulch, and the camp largely disappeared from public awareness. Former internees and their families nevertheless preserved memories, documents, and objects. The Japanese Cultural Center of Hawaiʻi and community researchers relocated the site in 2002 after sustained investigation. Archaeologists then mapped foundations, walls, roads, aqueduct features, and artifacts that survived beneath dense growth. Their work demonstrated that the landscape retained powerful material evidence even though most wartime structures were gone.

The federal government designated Honouliuli a national monument in 2015, and Congress redesignated it a national historic site in 2019. The National Park Service works with descendant communities, scholars, landowners, and local organizations to conserve the fragile site and develop access and interpretation. Honouliuli commemorates both civilians denied liberty and prisoners of war held under different legal regimes. Its history asks how national security, military rule, race, citizenship, and civil rights were negotiated in wartime Hawaiʻi—and why hidden places require deliberate recovery.