The Park was purchased by Mercer County in 1958 from the Broad Street Park Civic Association for $1.00  under the condition that the park would always remain a  passive environment with no active recreation. Birdwatching and fishing are its prime activities and is a popular area for birdwatchers and nature lovers throughout the region and the East coast.

The Delaware-Raritan Greenway has been instrumental along with several volunteers in keeping JAR in its pristine and natural state. Rider University conducts educational tours and classes at the Park.

• There are picnic tables and benches at the Spring Lake side of the park and a family picnic area at the marsh side of the park known as Watson's Woods
  
  
• Connected to over 8 miles of walking trails and 11 miles of water trails.
  
  
• At the Watson's Woods end of the facility is the Watson House, The house is on the National Historic Register and is the State Headquarters for the Daughters of the American Revolution. The interior of the house is furnished as Mr. Watson and his family may have lived over 300 years ago with a colonial kitchen and living area as well as antiquities that the Watson's brought with them from England.
  
  
• Nature and Interpretive Center-The County, in partnership with D & R Greenway Land Trust and the NJDEP Green Acres Program, has secured a home for this center at the Marsh located on Wescott Ave scheduled to open Spring of 2007.
  
  
• The role of the N & I Center is to promote an understanding of the contributions that wetlands make to regional biodiversity and the resources it provides to surrounding communities.
  
  
• Part of the impressive 1,250 acre Hamilton/Trenton Marsh is the northernmost freshwater tidal marsh on the Delaware River. The marsh includes both tidal and nontidal marshland, forested swamp and upland and second-growth forest. Ponds, creeks, and Delaware & Raritan Canal and the Delaware River are all connected by this extensive waterway.