Rocky Hill is a borough located in the southern portion of Somerset County, New Jersey, United States. As a small residential community, it covers an area of approximately 0.7 square miles and is situated along the Millstone River. It is bordered by Montgomery Township to the west and north, and Franklin Township to the east and south.
The settlement of Rocky Hill dates back to the early 18th century, developing around the local milling and quarrying industries facilitated by its proximity to the river and regional trap rock deposits. The borough was officially incorporated on December 18, 1889, from portions of Montgomery Township.
Historically, Rocky Hill is notable for its association with the American Revolutionary War. It is the site of Rockingham, the Berrien family farm which served as George Washington’s final wartime headquarters from August to November 1783. It was at Rockingham that Washington received news of the signing of the Treaty of Paris and where he penned his "Farewell Orders to the Armies of the United States." While the original house was moved several times to preserve it from quarrying activities, it remains a designated state historic site located just outside the borough's current borders.
The borough operates under a borough form of government, typical of many small New Jersey municipalities, consisting of a mayor and a six-member borough council. The community is primarily residential, with a small commercial district centered near the intersection of New Jersey Route 27 and County Route 518.
Demographically, Rocky Hill has maintained a relatively stable, small population throughout the late 20th and early 21st centuries. According to the United States Census Bureau, the population was 688 as of the 2020 Census. The borough is part of the Montgomery Township School District through a long-standing relationship, as Rocky Hill does not operate its own independent school system.
