The original section of this two-story schoolhouse was completed in 1887 to serve the Llano students living south of the river. Constructed of native sandstone and timber, it was known as the "College Building" because of the stately style. An addition to the north of the schoolhouse, built of locally-quarried granite, was completed in 1902. The school name was chosen to honor the noted Texas writer William Sydney Porter (O. Henry). The O'Henry School building housed all grades until 1925, when a separate high school structure was built.