Main Building was originally designed to house 200 patients of each gender, with the wards for the men extending from the south end of the central building and the wards for women extending north. Only half of the women's wing was ever completed.
The walls are red North River brick alternate with deep bluestone from the Catskills. The basement is rimmed with bluestone ashlar where it shows above the ground and the strings and windowheads are done in light Ohio sandstone and bluestone. Roof shingles are Susquehanna slate.
