Route 21 is a south–north state highway

State highway

State highway, state road or state route can refer to one of three related concepts, two of them related to a state or provincial government in a country that is divided into states or provinces :#A...

 in Massachusetts

Massachusetts

The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...

 that runs between Springfield

Springfield, Massachusetts

Springfield is the most populous city in Western New England, and the seat of Hampden County, Massachusetts, United States. Springfield sits on the eastern bank of the Connecticut River near its confluence with three rivers; the western Westfield River, the eastern Chicopee River, and the eastern...

 and Belchertown

Belchertown, Massachusetts

As of the census of 2000, there were 12,968 people, 4,886 households, and 3,517 families residing in the town. The population density was 245.9 people per square mile . There were 5,050 housing units at an average density of 95.8 per square mile...

.

Route description

The route begins at U.S. Route 20

U.S. Route 20

U.S. Route 20 is an east–west United States highway. As the "0" in its route number implies, US 20 is a coast-to-coast route. Spanning , it is the longest road in the United States, and the route sparsely parallels Interstate 90...

 in the Indian Orchard section of Springfield. It heads north, intersecting with Route 141

Massachusetts Route 141

Route 141 is a west–east state highway in the U.S. state of Massachusetts. Its western terminus is at Route 10 in Easthampton. Its eastern terminus is at U.S...

 before crossing the Chicopee River

Chicopee River

The Chicopee River is an tributary of the Connecticut River in Metropolitan Springfield, Massachusetts, known for fast-moving water and its extraordinarily large basin: the Connecticut River's largest tributary basin...

 into Ludlow

Ludlow, Massachusetts

Ludlow is a town in Hampden County, Massachusetts, United States. The population was 21,103 as of the 2010 census. It is located in western Massachusetts, north of Springfield, east of Chicopee, southeast of Granby, southwest of Belchertown, west of Wilbraham and is considered part of the...

. Once in Ludlow, the road continues in a northeasterly direction. It passes under the Massachusetts Turnpike

Massachusetts Turnpike

The Massachusetts Turnpike is the easternmost stretch of Interstate 90. The Turnpike begins at the western border of Massachusetts in West Stockbridge connecting with the Berkshire Connector portion of the New York State Thruway...

, with access to that road via Exit 7. It continues through town, passing south of the Springfield Reservoir before heading northward into Belchertown. In Belchertown it shares a concurrency with U.S. Route 202

U.S. Route 202

U.S. Route 202 is a highway stretching from Delaware to Maine, also passing through the states of Pennsylvania, New Jersey, New York, Connecticut, Massachusetts, and New Hampshire....

, which ends at Route 181

Massachusetts Route 181

Route 181 is a long north–south state highway in Massachusetts starting at the northern intersection of US 202 and Route 21 in Belchertown. The highway crosses Interstate 90 in Palmer, but there is no interchange. However, Exit 8 is nearby. Route 181 ends at US 20 in Palmer....

. From there Route 21 makes its final short trek to its current terminus at Route 9.

Prior to the completion of the Quabbin Reservoir

Quabbin Reservoir

The Quabbin Reservoir is the largest inland body of water in the Commonwealth of Massachusetts and was built between 1930 and 1939. Today along with the Wachusett Reservoir, it is the primary water supply for Boston, some to the east, as well as 40 other communities in Greater Boston...

, Route 21 extended further northward. It passed through the former town of Enfield

Enfield, Massachusetts

Enfield was formerly a town in Hampshire County, Massachusetts, incorporated in 1816 from portions of Greenwich and Belchertown. It was named in honor of one of its early settlers, Robert Field...

, then northward along the Swift River into Greenwich

Greenwich, Massachusetts

Greenwich was a town in Hampshire County, Massachusetts.It was established in 1739 as Quabbin, incorporated as Quabbin Parish in 1754 and became the town of Greenwich in 1754. It was located along the East and Middle branches of the Swift River...

 and the northern end of Dana

Dana, Massachusetts

Dana is a former town located in Worcester County, Massachusetts. Formed from parts of Petersham, Greenwich, and Hardwick, it was incorporated in 1801, and was disincorporated on April 28, 1938, as part of the creation of the Quabbin Reservoir. Upon disincorporation, most of the town was returned...

 before heading through the current town of Petersham

Petersham, Massachusetts

Petersham is a town in Worcester County, Massachusetts, United States. The population was 1,234 at the 2010 census. Petersham is home to a considerable amount of conservation land, including the Quabbin Reservation, Harvard Forest, the Swift River Reservation, and Federated Women's Club State...

 and into Athol

Athol, Massachusetts

Athol is a town in Worcester County, Massachusetts, United States. The population was 11,584 at the 2010 census.-History:Originally called Pequoiag, the area was first settled by five families in September 1735. When the township was incorporated in 1762, the name was changed to Athol...

, where it terminated at what is now Route 2A. The southern portion of the road (Old Enfield Road) is still accessible in Belchertown. The northern trunk follows Pleasant Street and New Sherborn Road in Athol, then the Monson Turnpike (Turnpike Road) in Petersham, where the road had an intersection with Route 122. Much of the route south of this intersection lies within the Quabbin Reservoir State Reservation.

Junction list

County	Location	Mile	Roads intersected	Notes
Hampden Hampden County, Massachusetts -Demographics:As of the census of 2004, there were 461,228 people, 175,288 households, and 115,690 families residing in the county. The population density was 738 people per square mile . There were 185,876 housing units at an average density of 301 per square mile...	Springfield Springfield, Massachusetts Springfield is the most populous city in Western New England, and the seat of Hampden County, Massachusetts, United States. Springfield sits on the eastern bank of the Connecticut River near its confluence with three rivers; the western Westfield River, the eastern Chicopee River, and the eastern...	0.0	U.S. Route 20 U.S. Route 20 U.S. Route 20 is an east–west United States highway. As the "0" in its route number implies, US 20 is a coast-to-coast route. Spanning , it is the longest road in the United States, and the route sparsely parallels Interstate 90... Route 141 Massachusetts Route 141 Route 141 is a west–east state highway in the U.S. state of Massachusetts. Its western terminus is at Route 10 in Easthampton. Its eastern terminus is at U.S...	Southern terminus of Routes 21 & 141; southern end of concurrency with Route 141
		1.2	Route 141 Massachusetts Route 141 Route 141 is a west–east state highway in the U.S. state of Massachusetts. Its western terminus is at Route 10 in Easthampton. Its eastern terminus is at U.S...	Northern end of concurrency with Route 141
	Ludlow Ludlow, Massachusetts Ludlow is a town in Hampden County, Massachusetts, United States. The population was 21,103 as of the 2010 census. It is located in western Massachusetts, north of Springfield, east of Chicopee, southeast of Granby, southwest of Belchertown, west of Wilbraham and is considered part of the...	2.3	I-90 Massachusetts Turnpike The Massachusetts Turnpike is the easternmost stretch of Interstate 90. The Turnpike begins at the western border of Massachusetts in West Stockbridge connecting with the Berkshire Connector portion of the New York State Thruway...	Mass Pike Exit 7
Hampshire Hampshire County, Massachusetts -Demographics:As of the census of 2000, there were 152,251 people, 55,991 households, and 33,818 families residing in the county. The population density was 288 people per square mile . There were 58,644 housing units at an average density of 111 per square mile...	Belchertown Belchertown, Massachusetts As of the census of 2000, there were 12,968 people, 4,886 households, and 3,517 families residing in the town. The population density was 245.9 people per square mile . There were 5,050 housing units at an average density of 95.8 per square mile...	12.0	U.S. Route 202 U.S. Route 202 U.S. Route 202 is a highway stretching from Delaware to Maine, also passing through the states of Pennsylvania, New Jersey, New York, Connecticut, Massachusetts, and New Hampshire....	Southern end of concurrency with US 202
		13.0	U.S. Route 202 U.S. Route 202 U.S. Route 202 is a highway stretching from Delaware to Maine, also passing through the states of Pennsylvania, New Jersey, New York, Connecticut, Massachusetts, and New Hampshire.... Route 181 Massachusetts Route 181 Route 181 is a long north–south state highway in Massachusetts starting at the northern intersection of US 202 and Route 21 in Belchertown. The highway crosses Interstate 90 in Palmer, but there is no interchange. However, Exit 8 is nearby. Route 181 ends at US 20 in Palmer....	Northern end of concurrency with US 202; northern terminus of Route 181
		13.73	Route 9	Northern terminus of Route 21 (Signed as U.S. Route 21)