In the early 1630s, a Praying Indian village named Shawshin was at the current site of Billerica, commonly spelled Shawsheen today, as in the Shawsheen River. In 1638, Massachusetts Bay Governor John Winthrop and Lt. Governor Thomas Dudley were granted land along the Concord River in the area, and roughly a dozen families from Cambridge and Charlestown Village had begun to occupy Shawshin by 1652. The settlers chose the name Billerica because some of the families originally came from the town of Billericay in Essex, England. The town was incorporated as Billerica in 1655, on the same day as neighboring Chelmsford and nearby Groton. The original plantation of Billerica was divided during the colonial period into the towns of Billerica, Bedford, Wilmington, and Tewksbury.
The oldest remaining homestead in the town is the Manning Manse built in 1696, which was also the residence of William Manning (1747–1814), the author of The Key of Liberty, a critique of Federalist policies. Other notable Revolutionary War era residents included Asa Pollard, the first soldier killed at the Battle of Bunker Hill, and Thomas Ditson, who was tarred and feathered in 1775 while on a visit to Boston after attempting to illegally purchase a musket from a British soldier. The song "Yankee Doodle" supposedly became a term of national pride instead of an insult because of this event. The town now celebrates "Yankee Doodle Weekend" every September.
According to the United States Census Bureau, the town has a total area of 26.4 square miles (68 km2), of which 25.9 square miles (67 km2) are land and 0.5 square miles (1.3 km2) (1.90%) is water.
Billerica has several small neighborhoods that form villages (or sections) of town. Those villages are Billerica Center, East Billerica, North Billerica, Nutting Lake, Pinehurst, West Billerica, River Pines, Riverdale, and South Billerica.
As of the census of 2000, there were 38,981 people, 12,919 households, and 10,244 families residing in the town. The population density was 1,505.9 inhabitants per square mile (581.4/km2). There were 13,071 housing units at an average density of 504.9 per square mile (194.9/km2). The racial makeup of the town was 94.68% White, 1.11% African American, 0.10% Native American, 2.76% Asian, 0.04% Pacific Islander, 0.33% from other races, and 0.99% from two or more races. Hispanic or Latino of any race were 1.54% of the population.
There were 12,919 households, out of which 37.4% had children under the age of 18 living with them, 66.1% were married couples living together, 9.4% had a female householder with no husband present, and 20.7% were non-families. 16.4% of all households were made up of individuals, and 5.3% had someone living alone who was 65 years of age or older. The average household size was 2.92 and the average family size was 3.30.
In the town, the population was spread out, with 25.7% under the age of 18, 7.3% from 18 to 24, 34.6% from 25 to 44, 24.0% from 45 to 64, and 8.4% who were 65 years of age or older. The median age was 36 years. For every 100 females, there were 103.5 males. For every 100 females age 18 and over, there were 102.2 males.
As of the 2010 census, the median income for a household in the town was $87,073, and the median income for a family was $95,128. The per capita income for the town was $32,517. About 2.8% of families and 3.8% of the population were below the poverty line, including 4.5% of those under age 18 and 4.3% of those age 65 or over.
Billerica was a contender for CNN Money's "Best Places to Live" in 2009 but did not make the top 100 list for the nation.
Billerica Public Schools operate primary and secondary schools. The Billerica public school system consists of five elementary schools, two middle schools, and one high school. A sixth elementary school, Eugene C. Vining Elementary, closed permanently at the end of the 2019 school year. In addition, the town is home to a regional technical high school. Shawsheen Valley Technical Highschool.
The Middlesex Canal, which flowed through Billerica between 1795 and 1852, was used to transport goods between Lowell and Boston.
In the 1840s, the Boston and Lowell Railroad's main line was built and passed through the town's villages of North Billerica and East Billerica. Stations were built in both locations and North Billerica station is still an active station on the MBTA Commuter Rail. Trains stopped taking passengers at East Billerica in 1965 and the station was remodeled and is now a private home.
E Ink Corporation, a privately held manufacturer of electrophoretic displays (EPDs) that powers tablets such as the Amazon Kindle and Barnes & Noble Nook.
Raytheon Company, a major American defense contractor and industrial corporation with core manufacturing concentrations in weapons and military and commercial electronics, has two large offices in Billerica.
EMD Serono, Inc, the US biopharmaceutical division of Merck Group, Darmstadt, Germany, a global pharmaceutical and chemical group, is undergoing a $75-million expansion of their Billerica facility, naming it the EMD Serono Research & Development Institute.
Cabot Corporation, a $3.3 billion specialty chemicals and performance materials company, has its primary Research and Development facility in Billerica.
Avaya Inc, a privately held $8 billion global provider of business communications and collaboration systems, has its New England headquarters in Billerica.
L3 Technologies, is a $15 billion American company that supplies command and control, communications, intelligence, surveillance and reconnaissance (C3ISR) systems and products, avionics, ocean products, training devices and services, instrumentation, space, and navigation products. They have a Billerica office on Concord Road.
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^"1920 Census of Population"(PDF). Bureau of the Census. Number of Inhabitants, by Counties and Minor Civil Divisions. Pages 21-5 through 21-7. Massachusetts Table 2. Population of Counties by Minor Civil Divisions: 1920, 1910, and 1920. Retrieved July 12, 2011.
^"1890 Census of the Population"(PDF). Department of the Interior, Census Office. Pages 179 through 182. Massachusetts Table 5. Population of States and Territories by Minor Civil Divisions: 1880 and 1890. Retrieved July 12, 2011.
^"1870 Census of the Population"(PDF). Department of the Interior, Census Office. 1872. Pages 217 through 220. Table IX. Population of Minor Civil Divisions, &c. Massachusetts. Retrieved July 12, 2011.
^"1860 Census"(PDF). Department of the Interior, Census Office. 1864. Pages 220 through 226. State of Massachusetts Table No. 3. Populations of Cities, Towns, &c. Retrieved July 12, 2011.
^"1850 Census"(PDF). Department of the Interior, Census Office. 1854. Pages 338 through 393. Populations of Cities, Towns, &c. Retrieved July 12, 2011.