narrower Taconic Range along the New York border. Upper tributaries of the Hoosic separate Massachusetts' highest peak, Mount Greylock from both ranges, however Greylock's geology connects it with the Taconics. Most of this region is a rolling upland of schist, gneiss and other resistant metamorphics with intrusions of pegmatite and granite. Scraping by continental glaciers during the Pleistocene left thin, rocky soil that supported hardscrabble subsistence farming before the Industrial Revolution. There was hardly a land rush into such marginal land, but the uplands were slowly settled by farmers throughout most of the 18th century and organized into townships. Then in the early 1800s better land opened up in Western New York and the Northwest Territory. The hilltown agricultural population went into a long decline and fields began reverting to forest. The Connecticut River Valley is an ancient downfaulted graben or rift valley that formed during the Mesozoic Era when rifting developed in the Pangaea supercontinent to separate North America from Europe and South America from Africa. Secondary rifts branched off the main crustal fracture, and this one was eventually occupied by the Connecticut River. The Metacomet Ridge is a series of narrow traprock ridges where lava penetrated this rift zone, beginning at the northern end of the graben near Greenfield and extending south across Massachusetts and Connecticut to Long Island Sound. Fossil dinosaur footprints in Holyoke attest to the life present in this region during the Mesozoic. As continental glaciers receded near the end of the last glacial period, a moraine at Rocky Hill, Connecticut, dammed the river to create Lake Hitchcock, extending northward some inundating places such as Springfield, Agawam, and West Springfield, while certain highlands remained above water, (i.e. sections of Holyoke). Accumulation of fine sediments during the era of Lake Hitchcock accounts for this region's exceptionally rich agricultural soil, which attracted settlers as early as 1635. Although the Connecticut River Valley's soil is the richest in New England, many of its fields have been covered by urban and suburban development. Regardless, the valley remains New England's most productive farmland. Tobacco, tomatoes, sweet corn, and other vegetables are still produced there in commercial quantities. Demographics Berkshire, Franklin, Hampshire and Hampden counties, in the year 2000 collectively had 814,967 residents, a population greater than that of any one of the six smallest U.S. states. The population amounted to approximately 12.84% of the 2000 population of the entire state