St. John's Academy was established on September 8, 1833 on Prince Street in Alexandria, Virginia by brothers William F. Carne and Richard L. Carne, along with Reverend John Smith, S.J.

In 1847, the school reopened under the leadership of Richard Libbey Carne Jr.

[9] The Academy initially had a reduction in students during the Civil War, but the number enrolled steadily increased to 154 in the 1863–64 school year.

[6] On March 29, 1870, an act of the Virginia General Assembly allowed for the state to loan arms to the Academy for students to drill as a volunteer militia.

[6] The Cadets participated in a number of special events, including the Centennial Exposition in 1876, Yorktown Centennial in 1881, Washington Monument Dedication in 1885, and the first inauguration of Grover Cleveland in 1885.