Essex County is located in the northeastern part of the U.S. state of New Jersey, and is one of the centrally located counties in the New York metropolitan area. As of the 2020 census, the county was the state's second-most populous county, with a population of 863,728, an increase of 79,759 (+10.2%) from the 2010 census count of 783,969, which in turn reflected a decrease of 1.2% (9,664 fewer residents) from the 793,633 enumerated in the 2000 Census. For 2021, the Population Estimates Program calculated a population of 854,917, which was ranked third of the state's 21 counties (with Middlesex County ranked second). Its county seat is Newark, with a 2020 census population of 311,549, making it the most populous city in the state.
In 2015, the county had a per capita personal income of $60,030, the eighth-highest in New Jersey and 153rd highest of 3,113 counties in the U.S. The Bureau of Economic Analysis ranked the county as having the 94th-highest per capita income of all 3,113 counties in the U.S. and seventh-highest in New Jersey in 2009. The county is part of the North Jersey region.