Pomona Catholic High School (originally called St. Joseph High School) was dedicated by James Cardinal Francis McIntyre, Archbishop of Los Angeles, in 1952. In 1954, the school received accreditation status with the Office of Relations with Schools – University of California. On April 1, 1979, Pomona Catholic became an Archdiocesan high school.
Eventually, to meet the needs of rapidly increasing enrollment, it was proposed that Pomona Catholic become an all girls’ school, and a boys’ high school be opened in the valley area. In 1958, the Old Bonita High School site was purchased by the Archdiocese and remodeled to meet modern standards. It officially opened in 1959 as Pomona Catholic Boys High School, later changing its name to Damien High School.