Elizabeth is both the largest city and the county seat of Union County, New Jersey, United States. As of the 2010 United States Census, the city had a total population of 124,969, retaining its ranking as New Jersey's fourth largest city (by population). The population increased by 4,401 (3.7%) from the 120,568 counted in the 2000 Census, which had in turn increased by 10,566 (+9.6%) from the 110,002 counted in the 1990 Census.