Elizabeth is a city in Union County, New Jersey, in the 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 was 126,179 as of the Census Bureau's 2006 estimate. 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.