FSX/Prepar3D – Trenton Mercer Airport (KTTN), New Jersey (NJ), USA. Trenton is a city in Mercer County, New Jersey, United States, which is the capital of the State of New Jersey and the county seat of Mercer County. The city is part of both the Greater New York City Combined Statistical Area and the Delaware Valley. As of the 2010 United States Census, Trenton had a population of 84,913, making it the states 10th-largest municipality. The Census Bureau estimated that the citys population was 84,899 in 2011. Installer and pics inside. By Fernando Angel Gonzalez.