Olney, originally patented as Prospect, is a historic home and farm complex located at Joppa, Harford County, Maryland. It is a 264-acre (1.07 km2) working pony farm with a collection of 15 structures ranging in style, use, and elegance. The main building on the property is a  2 1⁄2-story brick house dating to 1810, generally called "the mansion." The house was evolved into a museum of Maryland architecture, with salvaged features from demolished buildings in Baltimore and Philadelphia. These include paneling from the Isaac Van Bibber house in Fells Point, Baltimore dating to 1815; the marble Ionic portico from William Small's Baltimore Athenaeum from 1830; and a marble bas-relief plaque designed by Pierre L'Enfant for Robert Morris's great 1795 house in Philadelphia. Also on the property