In 1866, the school was moved for two years to Carroll Hall at 10th and G Streets. The Brothers returned to St. Matthew’s parish in 1868, when Father Charles White opened a new and larger school named St. Matthew’s Institute at the corner of 16th and L Streets.

The Brothers expanded the school once again when they purchased the estate of General Montgomery C. Meigs at 1225 Vermont Avenue and began construction of a school building in August, 1878. At first the school was known as St. John’s Institute, then as St. John’s Collegiate Institute, and, finally, in 1887 it was incorporated by the District of Columbia as St. John’s College, empowered to grant both the Bachelor and Master of Arts Degrees along with secondary school diplomas. The first Bachelor’s Degrees were conferred on six young men on June 24, 1892.

Largely through the efforts of Brother E. Alfred, F.S.C., the Cadet Corps was organized for the US Army by Major J. Dapray in 1915. Through the years, the Cadet Regiment has won recognition as an outstanding JROTC Unit.

In 1921, the Board of Trustees decided to discontinue the collegiate programs and devote the school to secondary education alone, although the school did conduct a School of Commerce and Finance at 13th Street and Massachusetts Avenue for some years.

While St. John’s was continued at Vermont Avenue, the Brothers purchased a property bounded by Rock Creek Park to house the freshman classes and provide athletic fields. Later, as the Vermont Avenue buildings became less useful, the decision was made to move the whole school to the Military Road site. The new St. John’s College opened its doors in September, 1959, and it is this chapter in the school’s history that continues to the present day.

In 1991, St. John’s started a new tradition by admitting young women to the institution for the first time in its 140-year history. The JROTC program also became an optional choice.