In 1866, Whipple opened a school for girls, St. Mary's Hall, in his home in downtown Faribault. The girls remained there until 1872 when Whipple moved to a new house and St. Mary's Hall was turned over to a board of trustees. By 1883, St. Mary's had also outgrown its downtown facilities, and a grand, ornate building, often called "the Castle on the Rhine", was built on the bluffs, less than half a mile south of Shattuck. That building burned in 1924, and the limestone structure that stands today was built less than a year later.