Ramona Convent of the Holy Names was founded in 1889 at Ramona Acres in Los Angeles County. This area was later called Shorb and is now part of the City of Alhambra. The Sisters of the Holy Names of Jesus and Mary came from Oakland at the request of several San Gabriel Valley families interested in the education of their daughters. Prominent among these parents were Mr. & Mrs. James de Barth Shorb, who donated about one-half of the thirty-one and a half acres which comprise the original property. In 1939, three acres were sold to the State of California for the Ramona Freeway, since renamed the San Bernardino Freeway. The first building to be built was a four-story red brick building on the knoll that dominated the Convent grounds. The dedication ceremony was presided over by the Right Reverend Bishop Mora of Los Angeles on January 29, 1890, and the first commencement exercises were held on June 23, 1891.
The groundbreaking ceremony for greater Ramona took place April 18, 1910. Three years later the new chapel was dedicated by the Right Reverend Bishop Conaty of Los Angeles. In the years that followed, other additions were made: the gymnasium, swimming pool, English Wing, Junior Living Room, Sisters' Residence, Holy Family Room, and Science Building. The 1967 Library Building, also housing a language laboratory center, and a computer lab was the first structure in the Master Plan.
In 1979, approximately four acres of the southwestern section of Ramona's property were sold in order to facilitate further implementation of the Master Plan. Consequently, additions to the Plan included, the 16-classroom building (Dufresne) and the multi-purpose gymnasium on Ramona Road. The buildings, dedicated in February of 1981, house the Arts, Mathematics, Social Studies, Physical Education and Theology departments.
Because of extensive damage caused by the October 1, 1987 earthquake, the main buildings built between 1889-1912 were demolished in December 1987. A one-story building to house administrative offices, kitchen and dining facilities, and a chapel was dedicated on November 12, 1989, the beginning of Ramona's second century of excellence.
Ramona received Blue Ribbon School of Excellence status from the U.S. Department of Education in 1983 and again in 1998.
In 1995-1996, portions of the sisters' convent were utilized for storage and offices. The school museum was moved there as well as the entire Development Department.