Passaic ( pə-SAY-ik or locally pə-SAYK) 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 (ranked 16th in 2010), an increase of 756 (+1.1%) from the 2010 census count of 69,781, which in turn reflected an increase of 1,920 residents (+2.8%) 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. Located north of Newark on the Passaic River, it was first settled in 1678 by Dutch traders, as Acquackanonk Township. The city and river get their name from the Lenape word "pahsayèk" which has been variously attributed to mean "valley" or "place where the land splits."