The county is named after Essex, a county in the East of England. Based on data from the 2010 census, Essex County is the 14th-most densely populated county in the United States, and was ranked second in the state.

The east side of Newark is the Ironbound, a working-class community. East Orange has the Presidential Estate neighborhood full of large one family homes. Beginning at about the turn of the century, this region led the state in the rebuilding and rehab of its housing stock. In the 2000s, Newark led the state in the issuance of building permits. Many reasons were cited: city-wide incentives to encourage construction development, an improving local economy, the rising demand of low-cost housing so close to Manhattan. Newark has since then become one of the fastest growing cities in the entire Northeast and reported a gain in median income and drop in poverty rate. 

Western Essex tends to be more suburban and affluent. Within this region are some of the most diverse and racially integrated municipalities in the state and nation, including Montclair, West Orange, South Orange and Maplewood. Many neighborhoods are well-known magnets for New Yorkers such as Glen Ridge, Montclair, Verona, South Orange and West Orange. The communities of Livingston, West Caldwell, South Orange, Maplewood, Millburn, North Caldwell, and Essex Fells are some of the wealthiest towns in the county.  Short Hills has a popular upscale shopping mall, The Mall at Short Hills located near affluent communities in Morris and Union counties