Perth Amboy is a city in northeastern Middlesex County, in the U.S. state of New Jersey, within the New York metropolitan area. As of the 2020 United States census, the city's population was 55,436. Perth Amboy is known as the "City by the Bay", referring to its location adjoining Raritan Bay. The earliest residents of the area were the Lenape Native Americans, who called the point on which the city lies "Ompoge".