The high school was established through the 1908 merger of Kawaiahao Seminary for Girls, founded in 1864, and Mills Institute for Boys, founded in 1892. Both schools were founded by missionaries, with the goal of teaching English to native Hawaiians, Japanese, Chinese and other nationalities. It was established that the school must remain Christian so long as the original land was in use. However, students are allowed to practice any religion of their choice. Even members of the Hawaiian royal family attended the schools. By opening its doors to students with no prejudice over race and class status, Mid-Pacific was a part of a growing movement toward greater social acceptance that was rarely seen in the repressive oligarchical control within the Territory of Hawaii.