Within the Commonwealth of Massachusetts, State Route 9 refers to a major state highway associated with the corridor between Pittsfield to the west and Boston to the east. At the western terminus of Route 9 is the intersection for which United States Route 7 exists north and south and United States Route 20 exists west and south. While United States Route 20 is directed in a southerly direction, Route 9 is headed more directly eastward, with particular locations beyond Pittsfield including Dalton, Windsor, Cummington, Goshen, and Williamsburg in the rural areas between the Berkshires to the west and Pioneer Valley to the east. The next major community is the City of Northampton, home to Smith College and traditionally serving as the county seat of Hampshire County, Massachusetts. After crossing the Connecticut River, the Town of Hadley is the next accessible community, with Mount Holyoke College located in the nearby town of South Hadley accessible via Route 47. Following the rural fringe community of Hadley, Massachusetts, is the City of Amherst, which officially prefers to be referred to as the “Town of Amherst” and is a community of three colleges: Amherst, Hampshire, and UMass Amherst. Though the campus of Amherst College is associated with Route 9, the highway actually serves the role of the northern campus boundary of the college. Belchertown and Ware are the next communities and the last within Hampshire County, with the highway routed along the southern edge of the Quabbin Reservoir effectively separating the Pioneer Valley and Worcester regions of the Commonwealth from one another.
Now in Worcester County, Route 9 is notable for serving the Central Massachusetts communities of West Brookfield, Brookfield, Spencer, and Leicester prior to reaching the Worcester city limits. Beyond Worcester, the state highway continues to serve the communities of Shrewsbury, southern Northborough, northern Westborough, Southborough, Framingham, (North) Natick, Wellesley, Newton, Brookline, and finally, Boston.