Union City is a city in the northern part of Hudson County, in the U.S. state of New Jersey. As of the 2020 United States census, the city was the state's 18th-most-populous municipality, with a population of 68,589, an increase of 2,134 (+3.2%) from the 2010 census count of 66,455, which in turn had reflected a decline of 633 (−0.9%) from the 67,088 counted in the 2000 census. As of the 2010 Census, among cities with a population of more than 50,000, it was the most densely populated city in the United States, with a density of 54,138 per square mile of land. The Census Bureau's Population Estimates Program calculated that the city's population was 65,366 in 2022, ranking the city the 590th-most-populous in the country. Union City was incorporated as a city by an act of the New Jersey Legislature on June 1, 1925, with the merger of Union Hill and West Hoboken Township. Two major waves of immigration, first of German speakers and then of Spanish speakers, greatly influenced the development and character of Union City. Its two nicknames, "Embroidery Capital of the United States" and "Havana on the Hudson", reflect important aspects of that history. Thousands visit Union City each year to see the nation's longest-running passion play. Union City is where Mallomars were first sold and the site of the first lunch wagon, built by Jerry and Daniel O'Mahoney and John Hanf, which helped spark New Jersey's golden age of diner manufacturing, for which the state is colloquially referred to by author Richard J.S. Gutman as the "diner capital of the world".