Acton’s history reflects the history of Massachusetts, New England, and the United States.

Acton was first settled by Native Americans who used the Assabet, Sudbury and Concord rivers for transportation and the fields for farming seasonal crops. There is evidence of Native American settlements in Acton which go back 7,000 years. When the colonists arrived in this area, the Native American population dropped dramatically due to European diseases for which they had no immunity.^{[citation needed]}

Concord was the first inland colonial town established in the Massachusetts Bay Colony. The original boundaries of Concord included all of Acton and residents used the Acton land as grazing fields for their animals. In 1639, the first homestead was built within the modern day boundaries of the town.

Acton was established as an independent town on July 3, 1735. Acton has held annual town meetings since 1735, the records of which are held at Acton’s Memorial Library.

Acton residents participated in the growing hostility with Great Britain by sending a list of grievances to King George III on Oct. 3rd, 1774. The anniversary of this day is celebrated in Acton as Crown Resistance Day.

At the beginning of the Revolutionary War, on April 19, 1775, a company of minutemen from Acton responded to the call to arms initiated by Paul Revere (who rode with other riders, William Dawes and Samuel Prescott, with Prescott the only one of the three who was able reach Acton itself) and fought at the North Bridge in Concord as part of the Battle of Lexington and Concord. The Acton minutemen were led by Captain Isaac Davis. When a company was needed to lead the advance on the bridge which was defended by the British regulars, Captain Davis was heard to reply, “I haven’t a man who is afraid to go.” The Acton men led because, unlike other militias there, they were fully equipped with bayonets.

The colonists advanced on the bridge; in the exchange of musket fire that followed, Captain Isaac Davis and Private Abner Hosmer of Acton were killed. Davis was the first officer to die in the American Revolutionary War. In Acton they refer to “the battle of Lexington, fought in Concord, by men of Acton.”

During the 19th century, Acton participated in the growing Industrial Revolution. By the mid-19th century, Acton was an industrial center for the production of barrels (cooperage). There were also a powder mill, three gristmills and four sawmills in town. The American Powder Mills complex extended downstream along the Assabet River and manufactured gunpowder from 1835 to 1940.

On October 1, 1844, the railroad came to Acton. The Fitchburg Railroad was routed through South and West Acton so that it could serve the mills. South Acton became a busy rail center and was the division point for the Marlborough Branch Railroad. With the railroad came increasing development in those areas. In addition to the Fitchburg Railroad, two others crossed the town: the Nashua and Acton, and the Framingham and Lowell. These two railroads shared a double track right-of-way that ran from West Concord (aka Concord Junction) through East Acton and then splitting in North Acton in the vicinity of Route 27 and Ledge Rock Way.

In 1874, the population of the town was almost 1700. The town established its first newspaper, The Acton Patriot, and the residents of West Acton formed the first library, The Citizen’s Library. In 1890, the Memorial Library was completed and given to the town by William A. Wilde as a memorial to the Acton soldiers who fought in the Civil War.

Acton is located at 42°29′N 71°27′W / 42.483°N 71.450°W / 42.483; -71.450. According to the United States Census Bureau, the town has a total area of 20.3 square miles (53 km²), of which 20.0 square miles (52 km²) is land and 0.3 square miles (0.78 km²), or 1.53 percent, is water. Almost all of Acton is forested, except for where it has been cleared for residential or agricultural use. Some forested areas have been put aside for special use by corporations.

The current geography of Acton was created when the last wave of glaciers retreated approximately ten thousand years ago. Acton has nine drumlins — hills which are composed of glacial till. In addition, Wills Hole and Grassy Pond are kettle ponds which were formed in depressions in the till formed by large blocks of ice.

Acton has two primary stream systems: the Nashoba Brook system including the incoming streams Butter Brook, Wills Hole Brook and Conant Brook and the Fort Pond Brook system including the incoming streams Guggins Brook, Inch Brook, Grassy Pond Brook, Pratt’s Brook and Coles Brook. Both stream systems empty into the Assabet River, which passes briefly through the town at its southern corner. Nagog Pond in the north, forms Acton’s border with the Town of Littleton and provides drinking water to the Town of Concord. A small artificial pond is at NARA Park in North Acton.

While Acton Center has been the civic center of the town since the revolution, the four other village centers earned their nomenclature from the names of their corresponding railroad station.

The current Master Plan for the town encourages development in the village centers in an attempt to prevent further sprawl and preserve open space in the rest of the town.

According to the 2010 census, there were 21,924 residents, a 7.84% increase from 2000 and 5,958 families residing in the town. The population density was 1,080.5 per square mile (417.0/km²). There were 8,530 total housing units, 96% of which were occupied, at an average density of 384.6 per square mile (148.5/km²). The racial makeup of the town was 77.3% White, 18.6% Asian, 1.1% African American, 0.1% Native American, 1.2% from other races, and 1.7% from two or more races.

Of the 8,187 occupied households, 42.7% had children under the age of eighteen living with them, 63.5% were husband-wife married couples living together. 23.0% of all households were occupied by individuals 65 years of age or older living alone. The age distribution of the population was 29.5% under the age of 18, 4.3% from 18 to 24, 31.5% from 25 to 44, 26.4% from 45 to 64, and 8.4% 65 years of age or older. The median age was 38 years. For every 100 females, there were 97.2 males. For every 100 females age eighteen and over, there were 94.2 males. For those age 25 years or older in Acton during the 2000 census, 97.2% had a high school degree or higher, 72.0% had a bachelor’s degree or higher, and 40.5% had a graduate degree or higher. Also, 98.0% were employed with a mean commute time of 31.0 minutes.

The median income for a household in the town was $133,532, and the median income for a family was $156,388. Males had a median income of $109,371 versus $48,113 for females. The per capita income for the town was $61,034. About 1.7% of families and 2.9% of the population were below the poverty line, including 2.4% of those under age 18 and 3.3% of those age 65 or over.

Acton had 2,041 Chinese Americans in 2010, a 151% increase from 2000 and the ninth largest Chinese population in Massachusetts.

In 2014, 25% of the residents of Acton were born outside of the United States. In 2000 this percentage was 14%.

Data is from the 2009–2013 American Community Survey 5-Year Estimates.

Acton uses the Open Town Meeting form of town government. The town charter specifies that the annual town meeting must begin on the first Monday in April. The selectmen may also call a special town meeting at other times of the year to consider other business. Citizens may force a special town meeting by submitting a petition signed by 200 registered voters to the town clerk. Anyone may attend Town Meeting but only registered voters may vote. Acton also has a water district, which is run separately from town government, as a public utility.

Acton’s elected officials include the following: the Board of Selectmen (5 members, 3-year terms), the Town Moderator (1 person, 1-year term), Acton members of the Acton-Boxborough Regional School Committee (7 members, 3-year terms), the Housing Authority (4 members, 5-year terms) and Memorial Library Trustees (3 members, 3-year terms). In addition, the town moderator appoints a finance committee (9 members, 3-year terms) which issues an opinion on each of the warrant articles presented to Town Meeting. In addition, a separate and independent branch of government, the Acton Water District, was established in 1912 and consists of three elected commissioners, an elected moderator, an elected clerk, an appointed district counsel, finance committee, Water Land Management Advisory Committee, and paid professional staff.

The town services are primarily funded through the residential property tax, which is subject to the limitations imposed by state statute known as Proposition 2½. The Water District is funded through water rates, connection fees and property rental. The Water District revenues, however, are not subject to Proposition ​2 ¹⁄₂.

On the state level, Acton is represented in the Massachusetts Senate by James “Jamie” Eldridge, and in the Massachusetts House of Representatives by Danillo Sena and Tami Gouveia. On the federal level, Acton is part of Massachusetts’s 3rd congressional district, represented by Lori Trahan. The state’s senior (Class I) member of the United States Senate is Elizabeth Warren. The junior (Class II) senator is Ed Markey.

The civic infrastructure grew to accommodate the increasing population. A Water District was established in 1912 and a town-wide Fire Department was established in 1913. Acton was the first town in the area to have water-bound macadam highways.

In 2005 a new Public Safety Facility was built that expanded space for the Police Department and provided for a Joint Dispatch area with the Fire Department.

The Acton Water District is a community public water supply that delivers drinking water to the majority (about 90 percent) of the residents of the town of Acton, Massachusetts. All of the water provided from the district comes from seven wells located within the town of Acton. The district’s system consists of 106 miles (171 km) of water main, four storage tanks, and water treatment facilities including aeration, activated granulated carbon (GAC), an advanced Zenon(R) filtration facility, plus fluoridation and state mandated chlorination.

Separate from the Water District, residents of Great Road (Route 2A) obtain their water from the mains running down their street, that connect Lake Nagog to the Concord water system. They are billed by Concord. The lake is in far North Acton, right up to the town line with Littleton, but Concord apparently has the water rights.

Most homes and businesses in Acton (approximately 80%) use private on-site sewage systems (i.e. septic tanks). Higher density developments such as condominiums and apartment buildings (approximately 10% of the town) use private sewers which go to small-scale private treatment plants.

In 2001, Acton completed its first public sewer system, which serves approximately 10% of the town, primarily in South Acton. A betterment fee is charged to property owners whose property is sited proximate to the sewage lines, whether or not they connect to the system.

Acton is five miles (8.0 km) from I-495 and ten miles (16 km) from I-95/Route 128. Routes 2, 2A, 27, 62, 111, and 119 run through town.

The MBTA Commuter Rail Fitchburg Line train stops at the South Acton station. Railroad service provided to Fitchburg, Leominster, Shirley, Ayer, Littleton, Concord, Lincoln, Weston, Waltham, Belmont, Cambridge, and Boston.

Yankee Lines provides a commuter bus service to Copley Square in Boston from the “77 Great Road Mall” in Acton on MA-2A and MA-119.

The Bruce Freeman Rail Trail provides a paved bicycle commuter option north to Westford, Chelmsford and Lowell. The Assabet River Rail Trail provides a connection south to Maynard. The trails do not have lighting and are not snowplowed.