On August 2, 1965, at the heart of City Central School at Velez Street, Cagayan de Oro rose City High School, manned by the school administrator, Mr. Pedrito D. Acac. Part-time faculty members held classes from five o'clock in the afternoon to eight-thirty in the evening daily, and offered non-academic subjects during Saturdays, in a five-year curriculum. City High School transferred to its new site at 8th-2nd Streets at Barangay Nazareth in 1990 where the DSWD-X and South City Central extension were stationed at that time. By that time, City High School ran two sessions, namely the day and night thereby catering not only to the working students, but also to the full-time professional students. In February 1993, Mr. Rogelio Q. Mabao took over as the school administrator of Cagayan de Oro National High School. During that time, Cagayan de Oro National High School offered SEDP, science school for future curricula which brought in its laurel as "The Most Effective and Efficient Secondary Public High School" in the Division of Cagayan de Oro. CDONHS opened an annex at Macanhan in 1999 through the initiative of Ms. Fe L. Pajo, the school administrator who assumed office in January 1997. It continued to offer three curricula, namely Revised Basic Education (RBEC), Special Science Curriculum and SPED for the deaf students in the city. CDONHS has been maintaining its title for two years as the "The Most Effective and Efficient Secondary Public High School" in the division from 2001-2003. Five of its teachers were named as "Outstanding Teacher in Division and District" in the persons of Ms. Tersita L. Jacobe, Ms. Fe A. Elevado, Ms. Jesusa R. Saloma, Ms. Sandy A. Flores, and Ms. Cristine J. Arjona.