The Keystone Building is found on Stolp Island in Aurora, Illinois. The four-story building features a ground floor dedicated to individual shops, each with a private entryway. The main (west) facade stretched on Stolp Avenue. It is irregularly shaped on its rear facade, as it is on a triangular lot. The north facade is long and the south is only long. The entry to the main building is found under a patterned terra cotta screen. There are five major bays on the first floor: three north of the entry and two south. The bays are separated by brick piers, as is the entryway. The upper three floors have identical exteriors with double hung windows between brick piers. An ornamental terra cotta cornice caps the building on the main facade. The building is built with brown glazed brick with flecks of iron, which provides some blue and green bits. A terra cotta belt course is found above the first floor. Each of the six piers on the main facade features a decorative terra cotta shield. There are additional shields decorating the cornice. Eight bronze and glass light fixtures above the first floor provide external illumination.
