Question: Amhert, Massachusetts, is a town located in the valley of the longest river in which region of the United States?

Context articles: Connecticut River Walk Park
Missouri River Valley
Vuka (river)
Beowawe, Nevada
Susquehanna River
San Joaquin River
Amherst, Massachusetts
Connecticut River
Cagayan River
Colorado River (Texas)

The Connecticut River Walk is partially constructed park and bikeway in Springfield, Massachusetts, United States, along the banks of New England's largest river, the Connecticut River.
 Currently, Springfield's section of this park is 3.7 miles long, running from Chicopee, Massachusetts to the South End Bridge in Springfield, Massachusetts.
 Unique features of the trail include its path alongside an active - and soon-to-be the United States' first high-speed - train line, making it a "rail-with-trail," and its passing in very close proximity to the Naismith Memorial Basketball Hall of Fame.
 The longest river in New England, the Connecticut River is the Knowledge Corridor's most prominent natural asset.
 For centuries it has been a source of regional identity and pride; however, currently most residents are cut off from it by Interstate 91 - a 1960s-era elevated highway, which has become a major inhibitor to Springfield's economic and recreational riverfront growth, especially in recent years.
The Missouri River Valley outlines the journey of the Missouri River from its headwaters where the Madison, Jefferson and Gallatin Rivers flow together in Montana to its confluence with the Mississippi River in the State of Missouri.
 At 2300 mi long the valley drains one-sixth of the United States, and is the longest river valley on the North American continent.
 The valley in the Missouri River basin includes river bottoms and floodplains.
Vuka is a river in eastern Croatia, a right tributary of the Danube river.
 At 112 km , it is the 13th longest river flowing through Croatia and it has a drainage area of 644 km2 .
 The river is located in Vukovar-Srijem County, in the Slavonia region.
 It empties into the Danube at the town of Vukovar, which got its name from the river.
Beowawe ( ) is a small town, misnomered on the internet as a ghost town, in Eureka County in northeastern Nevada in the western United States.
 It is the site of a mining operation and a geothermal power plant, and has a public library.
 "Beowawe" is a Paiute Native American word meaning "gate", so named for the peculiar shape of the hills close to town which gives the effect of a gateway opening to the valley beyond.
 The town is located at an elevation of 4695 ft , and is situated on State Route 306 5 mi south of Interstate 80.
 The Humboldt River runs through northern Nevada near Beowawe.
 At approximately 300 mi long, it is the second longest river in the arid Great Basin of North America.
 It has no outlet to the ocean, but instead empties into the Humboldt Sink.
The Susquehanna River ( ; Lenape: Siskëwahane) is a major river located in the northeastern United States.
 At 464 mi long, it is the longest river on the East Coast of the United States that drains into the Atlantic Ocean, via the Chesapeake Bay.
 With its watershed, it is the 16th-largest river in the United States, and the longest river in the early 21st-century continental United States without commercial boat traffic.
The San Joaquin River is the longest river of Central California in the United States.
 The 366 mi long river starts in the high Sierra Nevada, and flows through the rich agricultural region of the northern San Joaquin Valley before reaching Suisun Bay, San Francisco Bay, and the Pacific Ocean.
 An important source of irrigation water as well as a wildlife corridor, the San Joaquin is among the most heavily dammed and diverted of California's rivers.
Amherst ( ) is a town in Hampshire County, Massachusetts, United States, in the Connecticut River valley.
 As of the 2010 census, the population was 37,819, making it the largest municipality in Hampshire County (although the county seat is Northampton).
 The town is home to Amherst College, Hampshire College, and the University of Massachusetts Amherst, three of the Five Colleges.
 The name of the town is pronounced without the "h" ("AM-erst"), giving rise to the local saying, "only the 'h' is silent", in reference both to the pronunciation and to the town's politically active populace.
The Connecticut River is the longest river in the New England region of the United States, flowing roughly southward for 406 mi through four U.S. states.
 It rises at the U.S. border with Quebec, Canada, and discharges at Long Island Sound.
 Its watershed encompasses five U.S. states and one Canadian province, 11260 sqmi via 148 tributaries, 38 of which are major rivers.
 It produces 70% of Long Island Sound's fresh water, discharging at 19600 cuft per second.
The Cagayan River, also known as the Rio Grande de Cagayan, is the longest river in the Philippines and the largest river by discharge volume of water (followed by Rio Grande de Mindanao).
 It has a total length of approximately 350 km and a drainage basin covering 27753 km2 .
 It is located in the Cagayan Valley region in northeastern part of Luzon Island and traverses the provinces of Nueva Vizcaya, Quirino, Isabela and Cagayan.
The Colorado River is an 862 mi long river in the U.S. state of Texas.
 It is the 18th longest river in the United States and the longest river with both its source and its mouth within Texas.