The General John Frelinghuysen House is a fine example of Georgian residential architecture with extensive Federal and Greek Revival modifications. The house was the home of the Frelinghuysen family from 1801 to 1922. In 1970, Congressman Peter Frelinghuysen regained possession of the house and donated it to the Borough of Raritan. The house retains some of its original c. 1801 finishes, woodwork and door hardware, as well as an early brick smokehouse in its cellar.

The house now serves as the Raritan Public Library. The Trust grant funded structural repairs and conservation of deteriorated brickwork, the first phase of the library expansion needed to relieve the historic house of the heavy use it currently receives. All work was guided by a historic structure report also funded by this grant.