As the Erie region expanded, the hospital quickly outgrew its original three-story home, and by 1900 a new “Old Main” annex was established, followed by the creation of a nursing school (1901); yet another annex (E Building in 1911); a nurses home (1925) and a new diagnostic building and 65-bed maternity ward (1939). All of the new facilities were built on Saint Vincent's original Sassafras Street campus. After World War II came another round of expansion, and in the 1950s hospital leaders revealed plans to build a new, air-conditioned four-story inpatient center with diagnostic, X-ray, physiotherapy, lab and clinical facilities, and remodeling of business quarters.