Billerica (listen) is a town in Middlesex County, Massachusetts, United States. The population was 40,243 according to the 2010 census. It takes its name from the town of Billericay in Essex, England.
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.