After the attack on Pearl Harbor on December 7, 1941, Hawaii was placed under martial law. More than 150,000 Japanese Americans lived in the territory, comprising over a third of the population. Incarcerating them all, as was done on the West Coast, would have collapsed Hawaii's economy overnight. Instead, authorities selectively detained roughly 1,200 to 1,800 individuals deemed security risks -- community leaders, Buddhist priests, Japanese-language teachers, fishermen with knowledge of coastal waters. The first detainees were held at a camp on Sand Island in Honolulu Harbor, but that facility was temporary and exposed. By 1943, the Army needed something more permanent, more controlled, and more hidden. They chose a 160-acre site in Honouliuli Gulch, near Ewa and Waipahu, where the steep terrain and dense vegetation provided natural concealment.

The camp opened in March 1943, receiving internees transferred from Sand Island. An eight-foot dual barbed-wire fence enclosed the compound. Eight watchtowers overlooked the grounds, staffed by a company of military police under the supervision of Captain Siegfried Spillner. The interior was divided by additional barbed wire into separate sections for men and women, civilians and military detainees, and different nationalities. By August 1943, a Swedish Legation colonel inspecting the camp under the Geneva Convention counted 160 Japanese Americans and 69 Japanese nationals. But the camp's population was never solely Japanese. Over time, Honouliuli held more than 4,000 individuals, including Okinawans, Italians, German Americans, Koreans, and Taiwanese. Of the seventeen sites associated with wartime internment across Hawaii, Honouliuli was the only one built specifically for prolonged detention.

Among the internees was Sanji Abe, a legislator for the Territory of Hawaii who served his community in public office from 1895 until his death in 1982. Harry Urata, a music teacher, endured Honouliuli and was subsequently transferred to the Tule Lake War Relocation Center on the mainland. Their stories hint at the broader pattern of incarceration: the people detained were not saboteurs or spies but teachers, politicians, merchants, and fishermen whose crime was their ancestry. The camp also became Hawaii's largest prisoner of war facility, holding nearly 4,000 POWs at its peak. The isolated gulch, punishing in its heat and humidity, earned its grim nickname honestly. For the civilians held there, the injustice was compounded by the knowledge that their labor and loyalty had built the very territory that now imprisoned them.

When the camp closed in 1946, its structures -- built cheaply and for temporary use -- deteriorated quickly. The gulch's fast-growing tropical vegetation reclaimed the site within years. No markers were placed, no memorials built. The land changed hands several times, and in 2007 the Monsanto Corporation purchased it. For more than half a century, the camp's existence faded from collective memory. Then, in 2002, Jane Kurahara of the Japanese Cultural Center of Hawaii began searching for the site. Working from a wartime photograph, she identified an aqueduct in the background and traced it to Honouliuli Gulch. A National Park Service survey confirmed the site's significance, and it was found eligible for listing on the National Register of Historic Places.

On February 24, 2015, President Barack Obama designated Honouliuli a national monument by presidential proclamation. The John D. Dingell Jr. Conservation, Management, and Recreation Act, signed on March 12, 2019, redesignated it as a national historic site, a status that helps secure federal resources for preservation and public access. The Japanese Cultural Center of Hawaii and the University of Hawaii at West Oahu have worked to expand awareness and provide educational programming. The site remains largely undeveloped, without formal visitor services -- which, in its own way, preserves the sense of isolation and concealment that defined the camp's original purpose. Honouliuli stands as evidence that the incarceration of Japanese Americans during World War II reached every corner of the United States, including the very islands whose attack was used to justify it.