What is the main setting in the novel, The Water Cure?

It is unclear where the novel takes place, but Grace, Lia, and Sky believe they are living on an island because the outside world has become a dangerous place for women. They have lived most of their lives here; when the family arrived, Grace was two years old and Mother was pregnant with Lia. Sky was born ten years later on the island. As the girls were growing up, King and Mother ran a clinic on the island meant to rehabilitate women who had been damaged by men on the mainland. The rehabilitation program consisted of bizarre rituals and therapies. However, the women stopped coming, or began to be turned away, many years before the novel begins. The island is very hot, and consists of a beach and a forested area, with mountains in the distance. There is a barbed wire fence in the forest, and Grace learns from James at the end of the novel that the outside world is just beyond this fence - that the island is not an island at all.