Middlesex County, MA, was created on May 10, 1643, by the Massachusetts General Court. This court, the then highest court in Middlesex county land, ordered that the whole plantation within the area be divided into four equal shares. This gave birth to Middlesex County. Initially, land in Middlesex County contained the towns of Cambridge, Charlestown, Sudbury, Watertown, Medford, Woburn, and Reading. Land in Middlesex County, Massachusetts, has deep historical roots. This is the site where the first armed conflict of the American Revolutionary War happened on April 19, 1775. Before that, the first Middlesex County Registry of Deeds had been created in Cambridge in 1649.
Of Massachusetts's 14 counties, Middlesex is one of the eight that don't have a county government or county commissioners. This has been the case since July 1, 1998, when state agencies assumed all county functions. This happened after state laws were enacted to transfer county functions to the state government. Before the Middlesex County government dissolution, its executive branch was made up of three county commissioners elected by the public to serve four-year terms. The executive also consisted of a County Treasurer who served a six-year period.
However, despite the dissolution of the county government, records of land ownership in Middlesex continue to be handled by the initial Registries of Deeds. Before its abolition, some of the public offices that were part of the county government were the Middlesex District Attorney, the County Sheriff, Middlesex Clerk of Courts, and Middlesex Register of Probate. Holders of these officers were to be elected on a six-year term.
In the past years, government functions such as public education, property tax collection and assessment, road maintenance and repair, and elections were all handled at the municipal city level instead of the county government. The minimal functions of the county government are part of the reasons it was dissolved in 1998.

Middlesex County, Massachusetts, got its name from the Old English language. It was derived from the word "Middleseaxon," which means land of the Middle Saxons. Middlesex County is one of the original four counties in the state of Massachusetts. When the Massachusetts Bay Colony Genealogy began creating counties in early 1643, Middlesex was known as Middle Saxons. The county had no defined northern and western borders, with inhabitants moving freely from one town to another. However, in 1731, the borders were clearly defined after Worcester County was created on the west of Middlesex. The clarity of borders saw the county's name change from Middle Saxons to Middlesex, which has remained the case to date.