Boston is the largest city, located at the innermost point of Massachusetts Bay, at the mouth of the Charles River, the longest river entirely within Massachusetts. Most of the population of the Boston metropolitan area (approximately 5,800,000) does not live in the city; eastern Massachusetts on the whole is fairly densely populated and largely suburban.

Western Massachusetts is more rural and sparsely populated, especially in the Berkshires, the branch of the Appalachian Mountains that dominates the western quarter of the state. The most populated part of western Massachusetts is the "Pioneer Valley," alongside the Connecticut River, which flows across western Massachusetts from north to south.

Massachusetts was a center of the American Revolution, with actions by the patriots and counter-actions by the Crown (including the Intolerable Acts) a main reason for the unity of the Thirteen Colonies and the outbreak of war, starting with battles in and around Boston in 1775-76. Also see Boston Massacre, Boston Tea Party.

Battles of the American Revolution - Battles of Lexington and Concord, Siege of Boston, Battle of Bunker Hill.

First Governor of the Commonwealth - John Hancock was the first governor of the Commonwealth of Massachusetts.

Shays' Rebellion - Western Massachusetts uprising after the Revolution.

Slavery - Massachusetts was the first U.S. state to abolish slavery, in a 1783 judicial interpretation of its 1780 constitution. A 1790 census showed a slave population of zero.

District of Maine - On March 15, 1820, Maine was separated from Massachusetts, of which it had been a non-contiguous part, and entered the Union as the 23rd State.

U.S. Civil War - The 54th Massachusetts Volunteer Infantry was one of the first African-American regiments in the U.S. military.

The Central Artery/Tunnel Project (CA/T) - Known as the Big Dig to locals, it is the most expensive single highway construction project in the United States. The project began 1991, with final construction occurring in 2006.

The governor is head of the executive branch and serves as chief administrative officer of the state and as commander-in-chief of the Massachusetts National Guard. The current governor is Mitt Romney (Republican). All governors of Massachusetts are given the title His/Her Excellency, a carry-over from the Commonwealth's British past, despite titles being uncommon in American political traditions. Responsibilities of the governor include preparation of the annual budget, nomination of all judicial officers, the granting of pardons (with the approval of the governor's Council), appointments of the heads of most major state departments, and the acceptance or veto of each bill passed by the Legislature. Several executive offices have also been established, each headed by a secretary appointed by the governor, much like the president's cabinet.

During the first half of the 1900s, Boston was socially conservative and strongly under the influence of Methodist minister J. Frank Chase and his New England Watch and Ward Society, founded in 1878. In 1903, the Old Corner Bookstore was raided and fined for selling Boccaccio's Decameron. Howard Johnson's got its start when Eugene O'Neill's Strange Interlude was banned in Boston, and the production had to be moved to Quincy. In 1927, works by Sinclair Lewis, Ernest Hemingway, John Dos Passos, and Sherwood Anderson were removed from bookstore shelves. "Banned in Boston" on a book's cover could actually boost sales. Burlesque artists such as Sally Rand needed to modify their act when performing at Boston's Old Howard Casino. The clean version of a performance used to be known as the "Boston version." By 1929, the Watch and Ward society was perceived to be in decline when it failed in its attempt to ban Theodore Dreiser's An American Tragedy, but as late as 1935 it succeeded in banning Lillian Hellman's play The Children's Hour. Censorship was enforced by city officials, notably the "city censor" within the Boston Licensing Division. That position was held by Richard J. Sinnott from 1959 until the office was abolished on March 2, 1982. In modern times, few such puritanical social mores persist.

Massachusetts has since gained a reputation as being a politically liberal state and is often used as an archetype of liberalism. Massachusetts is the home of the Kennedy family of political fame and routinely votes for the Democratic Party in federal elections. Although Republicans have held the governor's office continuously since 1991, many of these (especially William Weld, the first of the recent lineage of Republican governors) are considered among the most liberal Republicans in the nation. Two of these governors, Paul Cellucci and Jane Swift, took office when their predecessors resigned to take other positions. Massachusetts has not voted for a Republican presidential candidate since 1984.

In presidential elections, Massachusetts supported Republicans until 1912, from 1916 through 1924, in the 1950s, and in 1980 and 1984. From 1988 through 2004, Massachusetts has supported Democratic presidential candidates, most recently giving native son John Kerry 61.9% of the vote and his largest margin of victory in any state. (It should be noted, however, John Kerry's margin of victory in the District of Columbia was much higher in 2004.) Every county in the Commonwealth supported the Democratic candidate.

Following a November 2003 decision of the state's Supreme Court, Massachusetts became the first (and so far only) state to issue same-sex marriage licenses on May 17, 2004. See the articles on same-sex marriage in the United States and same-sex marriage in Massachusetts.

Its agricultural outputs are seafood, nursery stock, dairy products, cranberries, and vegetables. Its industrial outputs are machinery, electrical and electronic equipment, scientific instruments, printing, and publishing. Thanks largely to the Ocean Spray cooperative, Massachusetts is the second largest cranberry producing state in the union (after Wisconsin). Other sectors vital to the Massachusetts economy include higher education, health care, financial services and tourism.

As of 2005, there were 6,100 farms in Massachusetts encompassing a total of 520,000 acres, averaging 85 acres apiece. Particular agricultural products of note include tobacco, animals and animal products, and fruits, tree nuts, and berries, for which the state is nationally ranked 11th, 16th, and 17th, respectively.

Massachusetts has a flat-rate personal income tax of 5.3%, with an exemption for income below a threshold that varies from year to year. The state imposes a 5% sales tax on retail sales of tangible personal property—except for groceries, clothing, and periodicals—in Massachusetts by any vendor. All real and tangible personal property located within the Commonwealth of Massachusetts is taxable unless specifically exempted by statute. The administration of the assessment and collection of all real and tangible personal property taxes in the Commonwealth of Massachusetts is handled by the city and town assessor and collected in the jurisdiction where the property is located. Massachusetts imposes a tax on any gains from the sale or exchange of capital assets held for more than one year. The state also collects a 12% tax on interest (except interest from Massachusetts banks), dividends, gains from the sale or exchange of capital assets held for one year or less (short-term capital gains). There is no inheritance tax and limited Massachusetts estate tax related to federal estate tax collection.