The Hosokawa family were sent first to an assembly center at the Puyallup, Washington fairgrounds where the family, along with others from the Seattle area, lived in horse stalls while the camps were being built. The family was moved to the Heart Mountain Relocation Center in Wyoming when he was 27 years old. Hosokawa's later writings and news reports were influenced by his time spent interned with fellow second-generation Japanese Americans, who were known as "Nisei", and their children, such as his son, who were known as "Sansei". Since Hosokawa had journalism and writing experience, he was appointed the editor of the Heart Mountain Relocation Camp newspaper, "The Heart Mountain Sentinel".