The idea of preserving the Princeton battlefield stretches back to the 1840s, but it was in 1897, when the local Mercer Engine Company No. 3 erected a granite monument with bronze plaque in honor of Gen. Mercer near the “Battlefield Farm” a farmhouse where Mercer died. Then, wealthy Princeton philanthropist Moses Taylor Pyne, who was largely responsible for transforming the small College of New Jersey into the prestigious Princeton University, was the first savior of the Princeton battlefield as well. His early efforts ensured that much of the battlefield remained untouched until someone got around to creating a battlefield park.

In 1899, when a trolley company intended to build a trolley line through the battlefield and the site of William Clarke’s home, Pyne bought property on the proposed right of way to stop the destruction, closing the deal with work crews on the site and ready   to get busy the next day.   Four years later, part of the battlefield was sold to developers, who planned new housing. Pyne stepped in and bought the land to protect it.  In 1921, three granite monuments with bronze tablets describing key events of the battle were installed on the battlefield, not by a local group, but the Oregon State Society of the Sons of the American Revolution. The land itself remained in private hands.

In 1946, Pyne’s long-sought battlefield park finally began to take shape when his granddaughter, Agnes Pyne Hudson, joined landowner Robert C. Maxwell to offer their 1777 battlefield land as gifts to the State of New Jersey. More than 1,000 people attended the dedication of the new 40-acre park on Oct. 20, 1946.  Over the years, the park has been enlarged and expanded a number of times with acquisitions and land donations. In 2017, the American Battlefield Trust (ABT) negotiated a land acquisition of 14.5 acres. The present state park is 81 acres. Coupled with the land purchased by the ABT, the battlefield is about 95 acres.