Massachusetts is the seventh-smallest state in the United States with an area of . It is bordered to the north by New Hampshire and Vermont, to the west by New York, to the south by Connecticut and Rhode Island, and to the east by the Atlantic Ocean and Gulf of Maine. Massachusetts is the most populous New England state.

Massachusetts is nicknamed "The Bay State" because of several large bays, which distinctly shape its coast: Massachusetts Bay and Cape Cod Bay, to the east; Buzzards Bay, to the south; and several cities and towns on the Massachusetts–Rhode Island border sit adjacent to Mount Hope Bay. At the southeastern corner of the state is a large, sandy, arm-shaped peninsula, Cape Cod, which forms the southern boundary of the Gulf of Maine to the north. The islands Martha's Vineyard and Nantucket lie south of Cape Cod, across Nantucket Sound. Central Massachusetts features rolling, rocky hills, while Western Massachusetts encompasses a fertile valley and mountains surrounding the Connecticut River, as well as the Berkshire Mountains.

Boston is Massachusetts' largest city, at the inmost point of Massachusetts Bay, the mouth of the Charles River. Most Bay Staters live in the Boston area, which covers most of eastern Massachusetts. Eastern Massachusetts is fairly densely populated and mostly suburban. Western Massachusetts features both the Connecticut River Valley—a fairly even mix of urban enclaves (e.g. Springfield, Northampton), and rural college towns (Amherst, South Hadley)—and the Berkshire Mountains, (a branch of the Appalachian Mountains) that remains mostly rural.

Massachusetts has 351 cities and towns. Every part of the state is within an incorporated city or town, but many towns include large rural areas. The state's 14 counties have few government functions and serve as little more than judicial districts.

Overview In Eastern Massachusetts, Boston is located at the innermost point of Massachusetts Bay, at the mouth of the Charles River. The Charles River is longest river located entirely within Massachusetts, (although the Westfield River can be considered longer if one combines its upper and lower branches); however, the Connecticut River is the Commonwealth's—and New England's—longest, and most significant river. Most of the population of the Boston metropolitan area (approximately 4.4 million) lives outside of the city proper. The City of Boston itself is densely urban. Generally, Eastern Massachusetts, including and surrounding Boston, is densely populated. Boston's suburbs stretch as far west as the City of Worcester in Central Massachusetts.

Central Massachusetts encompasses Worcester County, which is hilly and rocky. It features the urban city of Worcester, and the smaller cities of Fitchburg, Leominster, Gardner, and Southbridge. Central Massachusetts also includes many rural hill towns, forests, and small farms. The geographic center of Massachusetts is in the town of Rutland, in central Worcester County. The Quabbin Reservoir (formed by the dammed Swift River—a former Connecticut River tributary), borders the western side of the county; it is the main water supply for Greater Boston.The North Quabbin Woods: www.northquabbinwoods.org  (map; see text on map). Secretary of the Commonwealth of Massachusetts. Retrieved January 14, 2007.

The Connecticut River Valley features Massachusetts'—and some of the northeastern United States'—richest soil, due to Ice Age deposits by glacial Lake Hitchcock. The lower (southern) Connecticut River Valley features the city of Springfield, which sits a mere north of the Connecticut border at the confluence of three of Massachusetts' most significant rivers: the Connecticut (flowing north–south); the Westfield (flowing into the Connecticut from the west); and the Chicopee (flowing into the Connecticut from the east). Only separate Springfield from the State of Connecticut's capital city, Hartford—the Springfield-Hartford region is the second most populous region in New England (with approximately 1.9 million residents). Other cities in the Massachusetts portion of the New Haven-Hartford-Springfield arm of the Northeast megapolis include: Chicopee, Agawam, West Springfield, Westfield, Holyoke, and the college towns of Northampton, Amherst, and South Hadley.

Further west rises a range of rolling, purple mountains known as the Berkshires. Near the New York border, the Taconic and Hoosac Ranges cross into Massachusetts; however, in general, the area is known as The Berkshires. The region was populated by Native Americans until the 18th century when Scotch-Irish settlers arrived, after having found the fertile lowlands along the Connecticut River settled. On reaching the Berkshires, settlers found poor soil for farming, but discovered numerous fast-moving rivers for industry. Pittsfield and North Adams grew into small, albeit prosperous cities. A number of smaller mill towns exist along the Westfield and Housatonic Rivers, interspersed with wealthy vacation resort towns.

The National Park Service administers a number of natural and historical sites in Massachusetts. Along with twelve national historic sites, areas, and corridors, the National Park Service also manages the Cape Cod National Seashore and the Boston Harbor Islands National Recreation Area. In addition, the Massachusetts Department of Conservation and Recreation maintains a number of parks, trails, and beaches throughout the commonwealth.

Physical geography

Massachusetts extends from the mountains of the Appalachian system in the west to the sandy beaches and rocky shorelines of the Atlantic coast. The entire state was covered in ice during the Wisconsin glaciation, which shaped today's landscape. Much of the state remains covered in glacial till and dotted with typical glacial features, such as kettle ponds, drumlins, eskers, and moraines. Apart from a few alluvial floodplains, soils tend to be rocky, acidic, and not very fertile.

Part of the state is uplands of resistant metamorphic rock that were scraped by Pleistocene glaciers that deposited moraines and outwash on a large, sandy, arm-shaped peninsula called Cape Cod and the islands Martha's Vineyard and Nantucket to the south of Cape Cod. Upland elevations increase dramatically in Western Massachusetts. These uplands are interrupted by the downfaulted southern Pioneer Valley along the Connecticut River and further west by the Housatonic Valley separating the Berkshire Hills from the Taconic Range along the western border with New York. The highest peak in the state is Mount Greylock at near the northwest corner.

Topography Elevation and relief are greatest in the western part of the state and increase somewhat from south to north. The Taconic Mountains, part of the Appalachian system, run along the western border with New York, reaching at Mount Everett in the state's southwest corner, and including the state's highest point, Mount Greylock, at in the northwest corner. The Housatonic-Hoosic valley separates the Taconics from The Berkshires, a broad belt of steeply rolling hills that are a southern extension of the Green Mountains of Vermont. They extend south to the border of Connecticut. Mount Greylock lies on the western edge of the Taconic Range, across the Hoosic River from the Hoosac Range to the east. The Hoosac Range connects the Green Mountains with the Berkshires.Forest Physiography: Physiography of the United States and Principles of Soils in Relation to Forestry, Isaiah Bowman (New York: Wiley and Sons, 1911): p. 681.

Between the Berkshires and the rest of the state lies the Connecticut River Valley, known within Massachusetts as the Pioneer Valley. This ancient rift valley appeared in the Mesozoic Era when North and South America broke away from Europe and Africa. Dinosaur footprints near Mount Tom bear witness to that era, and series of basalt and sedimentary rock ridges (collectively known as the Metacomet Ridge) including Mount Toby, Mount Holyoke, Mount Tom, and others extending south to Long Island Sound and the valley's abrupt thousand-foot (300 meter) western escarpment illustrate the tectonic forces. More than a hundred million years later, as the Pleistocene epoch ended, receding glaciers left moraines that dammed the Connecticut River, creating Lake Hitchcock. Lacustrine silt deposits replaced soil scraped away by the glaciers, leaving behind deep, productive soil after the river breached the obstructing moraine and the lake disappeared.

East of this valley is an area of rolling uplands dotted with lakes and dissected by streams flowing into the Connecticut River in the west and into the Merrimack, Quinebaug, Blackstone, or Charles rivers, or into other shorter, coastal rivers in the east. Just to the east of the Pioneer Valley, hills rise steeply toward the divide between the Connecticut River basin and the river basins to the east. This divide runs through central Massachusetts, though the summit of Mount Wachusett, the highest point in the state east of the Connecticut River, rising to .

To the east of this divide, the elevation of the hilltops gradually decreases, and the landscape is more gently rolling. Within of the coast, few hills exceed in elevation. Near the coast, swamps, marshes, and ponds alternate with low hills. However, the Blue Hills, just south of Boston, rise above the surrounding landscape. The state probably takes its name from the Massachusett name for their highest point, Great Blue Hill, with an elevation of .

The Massachusetts coastline is deeply indented with bays, coves, and estuaries, separated by narrow promontories. Some of these form natural harbors that gave rise to the state's historic ports, including Newburyport, Gloucester, Salem, Boston, and New Bedford. The state has a few small barrier islands, the largest of which is Plum Island. The state's largest promontory is the Cape Cod peninsula. Its backbone is formed by glacial moraines, but much of its coastline has been shaped by the longshore drift of coastal sand, which forms many of its famous sandy beaches. To the south of Cape Cod, glacial moraines rise above the ocean surface to form the state's largest islands: Martha's Vineyard, Nantucket, the Elizabeth Islands, and Monomoy Island.

Climate

Massachusetts has a humid continental climate. Summers are warm, while winters are relatively cold, with average January temperatures below freezing throughout most of the state.

Generally, Massachusetts' hilly central interior (e.g. Worcester) and its western Berkshire Mountain region (e.g. Pittsfield) have colder winters than its coastal and Connecticut River Valley regions. Stockbridge, in the Berkshires, has a January average temperature of . In Eastern Massachusetts, Boston, on the coast of Massachusetts Bay, has an average January temperature of . The island of Martha's Vineyard has the state's highest average temperature—, due to the warming effect of the Atlantic Ocean. Summer temperatures are highest in the state's urban centers, due to the heat island effect. Average July temperatures in Massachusetts' three most populous urban centers are: Boston (coastal) - ; Worcester (central) - ; and Springfield (Connecticut River Valley) - . By contrast, the coolest average summer temperatures occur in the Berkshires and on the state's offshore islands. The average temperature in August, the warmest month on Nantucket Island, is . The average in July in Stockbridge is . Both daily and seasonal variation in temperature are greatest in the Berkshires and lowest along the coast.