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 five miles (8 km) 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.