Passaic is a city in Passaic County, in the U.S. state of New Jersey. As of the 2020 United States census, the city was the state's 16th-most-po…Passaic is a city in Passaic County, in the U.S. state of New Jersey. As of the 2020 United States census, the city was the state's 16th-most-populous municipality, with a population of 70,537, falling behind Bayonne, an increase of 756 from the 2010 census count of 69,781, which in turn reflected an increase of 1,920 residents from the 2000 census population of 67,861. The Census Bureau's Population Estimates Program calculated a population of 68,903 for 2023, making it the 552nd-most populous municipality in the nation. Among cities with more than 50,000 people, Passaic was the fifth-most densely populated municipality in the United States, with more than 22,000 people per square mile.