Locals call it the Monkey House. The decaying, three-story cement fortress sits among weeds in the wooded, hilly outskirts of Dongducheon, a Korean city of 96,000 that encircles Camp Casey, the closest U.S. military base to North Korea and home to key elements of the U.S. Army’s 2nd Infantry Division. The 2ID is “the only forward-based Army division integrated with Allied troops” in Korea, President Trump proudly declared to U.S. service members after his highly publicized crossing of the DMZ on June 30 to meet North Korean leader Kim Jong Un.

For those who live in Dongducheon, however, the base and surrounding town hold a mixed and painful legacy. Between the end of the Korean War and the early 1990s, more than one million Korean women were caught up in a state-controlled prostitution industry that was blessed at the highest levels by the U.S. military. They worked in special zones surrounding U.S. bases—areas licensed by the South Korean government, reserved exclusively for American troops, and monitored and policed by the U.S. Army. These camp towns were known to the Koreans as kichijong.

The system was designed to strengthen the U.S.-South Korean alliance, which was formalized in a 1954 Mutual Defense Treaty; its less formal mission was to boost morale for the thousands of U.S. military personnel stationed on the peninsula after the Korean War. It was the same for South Korea, where prostitution was encouraged as a woman’s patriotic duty to the state. Dongducheon, with some 7,000 registered prostitutes at its height, was the largest of the kichijong, and the strip of camp towns stretching from the DMZ down to Seoul was known as “GI Heaven.” For the Korean women in the camp towns, though, it was hell.

The Monkey House was a virtual prison for sex workers. It was built during a series of camp-town “cleanup” campaigns first launched by the South Korean government and the Pentagon in the 1960s. Their object was to ensure the sexual hygiene of American troops; rates of venereal disease among the GIs in South Korea were then far above the norm for American military installations in Japan and Europe. (In June 1971, a U.S. Army study found that 568 out of every 1,000 soldiers in Korea were infected with VD, compared to 111 per 1,000 worldwide.) Korean and U.S. security forces combed through the towns searching for women suspected of carrying STDs. Once in custody at the Monkey House, the women were inspected, shot up with penicillin supplied by the U.S. military, and confined inside its walls until they were “cured.” Then they were sent back to service their American customers.

The plight of women confined within these medical jails is the subject of a chilling graphic on the wall. The painting depicts the Monkey House and a giant vaginal inspection tool in front of a replica of a renowned image of three service members from the U.S.-controlled United Nations Command that still hangs inside Seoul’s Ministry of Defense. The source painting was commissioned as a tribute to the 16 countries that came to South Korea’s aid in 1950, but the grim repurposed image highlights the underside of the country’s long dependence on the United States. For anyone even casually versed in the long-standing U.S.-Korean alliance, this visual juxtaposition of state power and casual sexual predation pulls you up short. It’s like a silent scream against U.S. military power and sexual domination. “Lots of people are ashamed of what happened in the camp towns, and want to forget,” Choi said. “But people like me, we can’t forget. The U.S.-South Korean alliance depended on these comfort women.”