Designed in the late Romanesque Revival style by James Naughton and built in 1895 to handle the increasing student enrollment of P.S. 9 (today P.S. 340) across the street, the P.S. 9 Annex in Prospect Heights, Brooklyn is a brick and sandstone structure, featuring Italianate architectural elements including protruding dormers, towers and colonnettes, with accents of terra-cotta. In 1978, P.S. 9 Annex was listed on the National Register of Historic places and was converted into 22 co-op apartments in 1989.