Union City is a city in the northern part of Hudson County, New Jersey, United States. According to the 2010 United States Census the city had a total population of 66,455, reflecting a decline of 633 from the 67,088 counted in the 2000 Census, which had in turn increased by 9,076 from the 58,012 counted in the 1990 Census. The Census Bureau's Population Estimates Program calculated that the city's population was 67,982 in 2019, ranking the city the 540th-most-populous in the country.