In 1649, Ousamequin (Massasoit) sold the surrounding land, then known as Saughtucket, to Myles Standish as an addition to Duxbury. Brockton was part of this area, which the English renamed Bridgewater, until 1821, when it became the town of North Bridgewater. Its name changed in 1874, after a contentious process finally decided on naming it after Isaac Brock (the initial British commanding general at Queenston Heights, where invading American troops suffered a rout, in 1812), after a local merchant heard of Brockville, Ontario, on a trip to Niagara Falls. Brockton became a city on April 9, 1881. During the American Civil War, Brockton was America’s largest producer of shoes, and until the latter parts of the 20th century, Brockton had a large shoe and leather products industry.

According to the United States Census Bureau, the city has a total area of 21.6 square miles (56 km²), of which 21.5 square miles (56 km²) is land and 0.1 square miles (0.26 km²) (0.56%) is water. Brockton is the 162nd largest city by land area in the Commonwealth, and the twelfth largest of the twenty-seven towns in Plymouth County. Brockton is bordered by Stoughton to the northwest, Avon to the north, Holbrook to the northeast, Abington to the northeast, Whitman and East Bridgewater to the southeast, West Bridgewater to the south, and Easton to the west. Brockton is approximately 25 miles south of Boston, and 30 miles northeast of Providence, Rhode Island.

Brockton is mostly an urban setting, lying along the Salisbury Plain River, which once powered the many shoe factories of the city. To the northeast lies the Beaver Brook Conservation Land, attached to the southern end of the Ames Nowell State Park in Abington. There are several parks throughout the city, but the largest is D.W. Field Park, an Olmsted-inspired park which includes ponds, Waldo Lake and Brockton Reservoir in Avon, as well as a golf course.

As of the census of 2019, there were 95,705 people, 31,440 households, and about 3.04 people living in each household, and about an average family size of 3.59. The population density was 4,486.3 people per square mile. The racial makeup of the city was 27.3% White, 50.9% African American, 0.7% Native American, 2.0% Asian, 0% Pacific Islander, and 2.2% from two or more races. Hispanic or Latino of any race were 11.9% of the population. The African-American population in Brockton has grown significantly since the beginning of the early 2000s.

Brockton has one of the largest population of Cape Verdean ancestry in the United States, with about 9% of its population. Brockton also reportedly has one of the largest communities of Angolans in the United States.^{[citation needed]}

Statistically, Brockton is the most populous and most densely populated community in Plymouth County. It is the sixth largest community in the commonwealth, the largest of the sub-100,000 person cities. However, it is only the twenty-seventh most densely populated community in the Commonwealth.^{[citation needed]}

As of 2010, there were 33,675 households, out of which 35.0% had children under the age of 18 living with them, 42.0% were married couples living together, 19.9% had a female householder with no husband present, and 32.4% were non-families. 26.6% of all households were made up of individuals, and 9.5% had someone living alone who was 65 years of age or older. In the city, the population was spread out, with 27.8% under the age of 18, 9.1% from 18 to 24, 30.5% from 25 to 44, 20.8% from 45 to 64, and 11.7% who were 65 years of age or older. The median age was 34 years. For every 100 females, there were 92.1 males. For every 100 females age 18 and over, there were 87.4 males.

As of 2018, the median income for a household in Brockton is $55,140. Males have an average income of $41,093 versus $35,145 for females. The per capita income for the city was $17,163. The poverty rate in Brockton is 15.61% of the population. Notably by race, 23.55% of Hispanics were in poverty, while the Black population of Brockton had about 18.61% of its population living in poverty.

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

On the national level, Brockton is a part of Massachusetts’s 8th congressional district, and has been represented since January 2013 by Stephen Lynch.

On the state level, Brockton is represented in three districts in the Massachusetts House of Representatives: the Ninth Plymouth, Tenth Plymouth (which includes West Bridgewater and Precinct 1 of East Bridgewater), and the Eleventh Plymouth (which includes most of Easton). The city is represented in the Massachusetts Senate as a part of the Second Plymouth and Bristol district, which includes Halifax, Hanover, Hanson, Whitman and portions of East Bridgewater and Easton

Brockton has a city government led by a mayor and city council. The city elects a mayor for two-year terms. Previous mayors include Winthrop H. Farwell Jr., John T. Yunits Jr., David Crosby, Carl Pitaro, Richard L. Wainwright, John E. Sullivan, Alvin Jack Sims, Joseph H. Downey and Paul Studenski. James Harrington was elected mayor in 2005 and began his term in January 2006. He was re-elected on November 6, 2007, for another two-year term. He had previously served 16 years as a City Councilor. In the fall of 2009, City Councilor Linda Balzotti defeated Harrington to become the city’s first female mayor. Balzotti was defeated in 2013 by Bill Carpenter who won the election by only 44 votes. After the unexpected death of Bill Carpenter on July 3, 2019, Moises Rodrigues was elected unanimously by the 11-person City Council to become acting mayor of Brockton. On July 15, 2019 Moises Rodrigues became the first person of color to become Mayor of Brockton after serving six years on the Brockton city council. In 2009, community activist Jass Stewart was elected to councilor-at-large becoming the first African American to serve in Brockton’s city council. The city council consists of four Councilors-at-Large and seven ward Councilors, one for every ward in the city. As of January 2020, the mayor of Brockton is Robert F. Sullivan.