Essex County is a county in the northeastern part of the State of Massachusetts. As of the 2010 census the total population was 743,159, making it the third most populous counties in Massachusetts. It is a part of the Greater Boston area. The largest city in Essex County is Lynn. The county was named after the English county of Essex. [Essex is a county in the East of England immediately north-east of London and is one of the home counties. It borders the counties of Sulffolk and Cambridgeshire to the north, Hertfordshire to the west, Kent across the estuary of the River Thames to the south and London to the south-west. The county town is Chelmsford, which is the only city in the county.]
It has two county seats: Salem and Lawrence. Prior to the dissolution of the county government in 1999, Salem had jurisdiction over the Southern Essex District and Lawrence over the northern Essex District, but currently these cities do not function as seats of government. However, the county and the districts remain as administrative regions recognized by various governmental agencies, which gathered vital statistics or disposed of judicial case loads under these geographic subdivisions, and are required to keep the records based on them. The county has been designated the Essex National Heritage Area by the National Park Service.
The county was created by the General Court of the Massachusetts Bay Colony on May 10, 1643, when it was ordered "that the whole plantation within this jurisdiction be divided into four sheires". Named after the county in England, Essex then comprised the towns of Salem, Lynn, Wenham, Ipswich, Rowley, Newbury, Gloucester and Andover in 1680, two towns from Massachusetts' colonial era Norfolk County, Haverill, and Salisbury, both located north of the Merrimack River were annexed to Essex County. These ten large founding settlements were then subdivided over the centuries to produce Essex County's modern composition of cities and towns.
Essex County is famous as the area that Elbridge Gerry, who was born and raised in Marblehead, districted into a salamander like shape in 1812 that gave rise to the work gerrymandering.