Elizabeth is a city in Union County, New Jersey, United States. As of the 2000 census, the city had a total population of 120,568, making it New Jersey's fourth largest city (by population). The population of Elizabeth increased to a record high of 124,969 at the 2010 United States Census. It is the county seat of Union County. In 2008, Elizabeth was named one of "America's 50 Greenest Cities" by Popular Science magazine, the only city in New Jersey selected.