The town was named for Chelmsford, England, a substantial and interesting old town, twenty-nine miles from London, in the County of Essex, and containing a population of 13,000 (about 1896). It was named from the river Chelmer which flows through it. President John Adams, while visiting Chelmsford, England, in 1786 wrote in his diary: Chelmsford was probably named in compliment to Mr.  Hooker, who was once minister of that town in Essex, but afterwards in Holland, and after that at "Newtown" (Cambridge) and after that at Hartford, in New England. The Mr. Hooker referred to was Rev. Thomas Hooker, the  founder of Connecticut and the author of "the first written constitution known to history that created a government, and it  marked the beginning of American democracy, of which Thomas Hooker deserves more than any other man to be called the father. While it would be pleasant to see that the fathers of Chelmsford were prompted in giving it a name, by their admiration for this  enlightened statesman and preacher, it is to be remembered that Hooker left Cambridge for Connecticut nearly twenty years before Chelmsford was settled, and there is no evidence that he ever had any connection with the town.   

It was undoubtedly named, in accordance with the custom of the time, for the town in England which had been the former  home of some of the prominent settlers. An examination of a transcript of St. Mary's parish register, Chelmsford, England, in the possession of Mayor F. Chancellor, made by Walter Perham in 1902, shows that there were in the old mother town, between 1538 and the time of the settlement of this town, families or individuals bearing the names Adams, Butterfield, Spaldyng, Chamberlyne, Fletcher, Parker, Warren and Purkis, perhaps our  Parkhurst-names that have been prominent in the affairs of the Town, and its offshoots, from its earliest days to the present. 

Life and Works of John Adams, Vol. 3, p. 404,  John Fiske.

Chelmsford is the only town of that name  in the United States. There is, however, a Chelmsford in Ontario, Canada, and another in Northumberland County, New Brunswick.

Excerpt from the History of Chelmsford, Massachusetts, by Wilson Waters, 1913