Historic Prospect Hall For Sale or Lease. Building sits on a beautiful 4 acre parcel located on the west and north of interstates I-270 and I-70. The mansion dates to 1787 and is a nationally registered historic structure. It is positioned on the highest point within City of Frederick. Exterior has just been renovated. There is also a 1.8-acre parcel next to the property available for an additional $200,000. Contact Broker for additional information regarding property.