- Trenton is the capital city of the U.S. state of New Jersey. It is located in Mercer County and is situated along the Delaware River. Trenton is known for its rich history, as it played a pivotal role during the American Revolutionary War. The city is home to several historic landmarks and museums, including the New Jersey State House, Old Barracks Museum, and Trenton City Museum at Ellarslie Mansion. Trenton is also recognized for its diverse arts and cultural scene, with various theaters, galleries, and music venues. Additionally, the city hosts numerous annual events and festivals, such as the Trenton Punk Rock Flea Market and Patriots Week.