Delone Catholic High School is a regional high school named for Charles J. Delone, Esq., a prominent Catholic attorney of Hanover, who donated the land and the funds for the construction of the original building. The facilities that had been the education center for elementary and high school were destroyed by fire in 1938 which precipitated Mr. Delone's generous donation. The cornerstone of the new school was laid in 1939 and the new building was dedicated by Archbishop Amleto Giovanni Cicognanni, Apostolic Delegate to the United States, on Sept 2, 1940. As a tribute to Mr. Delone, the school bears his name and its athletic teams have adopted his title "Squires" and "Squirettes."

Father Cyril J. Allwein was appointed the first Principal of Delone Catholic High School. The Sisters of Saint Joseph were joined on the faculty by the Sisters of Mercy and, in 1941, by the Sisters of Christian Charity. In 1952 the high school was accredited by the Middle States Association under the direction of Father William R. Lyons, Principal 1948-1977. Two additional wings were added to the original building in 1955 and in 1963. A chapel, bearing the title, "Our Lady, Queen of Peace," was constructed in 1966. The chapel was moved in 2007 and renovated through a gift from the estate of Donald W. and Mary E. Small. The Lawrence B. (Sonny) Sheppard, Jr. Memorial, a gymnasium complex, the gift of Mr. and Mrs. L. B. Sheppard in memory of their son, was built in 1968. The 1963 Science and Math wing was renovated in the summer of 2011. The 1940 building received a complete renovation in the summer of 2013 and the 1955 wing, library, cafeteria, band room and old gym were renovated in 2016 and 2017.

Delone Catholic High School continues to serve the youth of parishes in Hanover, McSherrystown, Littlestown, Spring Grove, Abbottstown, New Oxford, Bonneauville, Gettysburg, Fairfield, Westminster, Emmitsburg, Reisterstown, Taneytown and Glyndon as well as non-Catholics from the Adams/Hanover area and northern Maryland. There are also international students from several countries enrolled at Delone Catholic.

Archbishop Amleto Giovanni Cicognanni, Apostolic Delegate to the United States dedicates Delone Catholic High School on Sept 2, 1940