Following its 19th century use for agricultural purposes, the East Campus became home to a first group of buildings in 1902. The buildings referred to as the Richardson Group or the 1902 Buildings, were part of the largest expansion in the history of both campuses.
The four two-story red brick buildings built on the East Campus for lack of space on the West Campus followed the same Italian Renaissance Revival styling as the older buildings of the West Campus and are exquisitely detailed with central cupolas, exposed rafter tails, brick chimneys, and rounded columns topped with red tile hipped roofs. These four buildings are referred to in campus references as R Building (Building 89), I Building (Building 95), N Building (Building 94), and P Building (Building 100).
The next significant East Campus development came in the 1930s with the construction of the larger buildings around Maple Square which would house the acute physical and mental treatment centers for the hospital. Their construction represents the shift to the scientific treatment of patients in the field and the move toward training interns at St Elizabeths Hospital. These buildings maintained the Italian Renaissance Revival style with their red brick and red tile roofs of the 1902 buildings, but on much larger structures.
While the scientific buildings were being developed at Maple Square, a new complex of patient residences was also being built southeast of the Richardson Group. Called the Continuous Treatment (CT) buildings, they were designed in the new cottage form and comprised six two-story residential structures (Buildings 106, 107, 108, 110, 111, and 112) surrounding a central kitchen and cafeteria (Building 109). All the buildings were connected to the cafeteria by two-story covered brick walkways. This complex continued the Italian Renaissance Revival style of the rest of the campus, with red brick and hipped red tile roofs, but fewer decorative details.
The final phase of East Campus construction (excluding the most recent facility, built on the far Eastern parcel of the East Campus) came in the 1950s and early 1960s. Three large institutional buildings were built in the East Campus study area after 1940: Building 119 in 1952, Building 122 in 1959, and Building 124 in 1963.