The Berkshires form a 150-mile (240 km) north–south highland corridor along the western edge of Massachusetts, extending from the Vermont border near Williamstown down to the Connecticut line at the Housatonic River valley. Geologically, they are the southern continuation of the Green Mountains, composed of metamorphosed Precambrian and Paleozoic rocks thrust upward during the Taconic and Acadian orogenies.
Northern hardwood forest (sugar maple, beech, yellow birch) transitions to oak-hickory at lower elevations. Over 100,000 acres of state forest and wildlife management areas support hiking (Appalachian Trail traverses 90 miles here), backcountry skiing, fly fishing, and leaf-peeping tourism each autumn.
Formerly mill- and agriculture-based, the economy now leans on cultural tourism, second-home ownership, healthcare, and education (Williams, MCLA, Bard College at Simon's Rock). The region markets itself as a year-round destination: music & theatre in summer, foliage in fall, skiing & museums in winter, garden tours in spring.