Paterson is the largest city in and the county seat of Passaic County, in the U.S. state of New Jersey. As of the 2020 United States census, the ci…Paterson is the largest city in and the county seat of Passaic County, in the U.S. state of New Jersey. As of the 2020 United States census, the city was the state's third-most-populous municipality, with a population of 159,732.