When Chelmsford was incorporated, its local economy was fueled by lumber mills, limestone quarries, kilns.

The farming community of East Chelmsford was incorporated as Lowell in the 1820s; over the next decades it would go on to become one of the first large-scale factory towns in the United States because of its early role in the country's Industrial Revolution.

Successive Pennacook leaders Passaconaway and Wonalancet strove to maintain a friendship with the European settler-colonizers who founded Chelmsford within their territory.

[5] Despite this determinedly pro-peace stance, Chelmsford settlers became increasingly violent towards the tribe, often forcing the Pennacook to flee north temporarily or permanently.

On one notable occasion, a handful of Pennacook who were too sick or elderly to flee with their kin remained behind and Chelmsford settlers burnt them alive in their dwelling.

[5] Eventually most Pennacook refugees permanently moved north to join relations in Odanak, but their descendants among the Abenaki First Nation and other tribes of the Wabanaki Confederacy continue to view Chelmsford as part of their ancestral and unceded homeland.

[8] In 1691, Martha was held in the Boston Gaol for witchcraft, appeared in court, but was eventually set free after about a month.

The Lieutenant Colonel Moses Parker Middle School honors his name, and the lobby displays a representation of the man.

The Chelmsford brand of golden ginger ale continued to be manufactured by Canada Dry for decades.

[35] The Fay A. Rotenberg School, a juvenile correctional facility for girls operated by the Robert F. Kennedy Children's Action Corps, Inc. on behalf of the Massachusetts Department of Youth Services, first opened in North Chelmsford in 1982; this facility had 16 beds.

Data below are from Massachusetts Department of Elementary and Secondary Education (ESE);[39] class sizes are for 2008–2009 school year.

All expenditures considered, the Chelmsford public schools district spent $10,070 per pupil as of 2008, which was lower than the state average of $12,449.

As of 2008 per-pupil allocation, $3,937 went to classroom and specialist teachers, $333 to administration, and $185 to instructional materials, equipment and technology.

The ranking took into account many statistics associated with quality of education and academic performance, including the school's 14.5:1 student–teacher ratio.

[43] Chelmsford High School performed significantly better than the state average in the English, math and science portions of the 2009 Grade 10 MCAS tests, scoring 89, 87 and 77 out of 100, respectively.

The heart of the town center is Central Square - the junction of routes 4, 110, the end of 129, and Westford Street.

This rotary was the cause of many accidents that occurred due to its small overall size and ability for vehicles to gain speed.

The line currently serves as a major corridor of Pan Am Railways' District 3 which connects New Hampshire and Maine with western Massachusetts, Vermont, and New York.

[45] The Bruce Freeman Rail Trail runs 6.8 miles (10.9 km) through Chelmsford, including the Central Square intersection.