With the support of the Episcopal Diocese of North Carolina, Smedes founded Saint Mary's as a school for young ladies "designed to furnish a thorough and excellent education equal to the best that can be obtained in the city of New York, or in any Northern school." The school was founded on the site of the Episcopal School of North Carolina, a short-lived school for boys in the 1830s. Three of the present school buildings—East Rock, West Rock and Smedes Hall—formed the original campus. East Rock and West Rock, the first two buildings, were constructed with remnant stones from the construction of the North Carolina State Capitol.
