The Vermonter was preceded by an overnight train between Montreal and Washington that was known as the Montrealer. In the days before Amtrak the Montrealer was a service of the Boston and Maine Railroad. Another train, the Ambassador ran the same route during the daytime, but terminated in New York City. Both services used the Boston and Maine's Connecticut River Line south of Vernon, Vermont, rather than the current route over the New England Central.
The Vermonter replaced the Montrealer on April 1, 1995, bringing daytime Amtrak service to Vermont.
Business Class was added to replace the sleeping cars that were taken out of service upon the change to the Vermonter. The route was changed to allow travelers from Vermont to again stop in Springfield and Hartford. This was made possible by the use of cab cars or locomotives on both ends so that the train could travel east from Springfield to Palmer, Massachusetts, and reverse direction to continue north on the Central Vermont. This detour added an hour of running time, but at the time was judged more practical than seeking to use the direct route over the former Boston and Maine Railroad owned by the Guilford Rail System. The train travels from Washington to New Haven on the Northeast Corridor, where electric locomotives are substituted for the diesel locomotives used north of that location.
Vermont declined to pay for continuing the Vermonter to Montreal due to high labor and terminal costs in Montreal. For a time Amtrak offered passengers a connecting Thruway bus service, operated by Vermont Transit, which met the train at St. Albans for connections to and from Montreal. Ridership plunged when the train schedule was moved two hours earlier, requiring a southbound departure before 5:00 a.m. The schedule was returned to its previous position, but the service was dropped by Vermont Transit (which had been running it without a subsidy as part of its regular schedule) on October 30, 2005.
On October 30, 2006, the Vermonter began stopping at the towns of Wallingford and Windsor Locks (near Bradley International Airport) in Connecticut for the first time in its existence.
In the late 2000s, Amtrak and the state of Vermont considered the purchase of diesel multiple unit (DMU) trainsets for use on the New Haven–St. Albans stretch of the line, with Amtrak offering a $2 million grant to help make the switch and market the new service. The new cars would purportedly have saved $4.25 million over three years, being four times more fuel efficient than a locomotive-hauled train. In 2008 the Vermont state legislature approved the purchase of five cars from Colorado Railcar at the cost of $18.2 million, but the company closed while the decision was awaiting approval of Governor Jim Douglas. With no other DMU designs available that were capable of operating in mixed traffic with other trains the plan was dropped.
On November 9, 2010, the State of Vermont, Amtrak, and New England Central began a $70 million project to increase train speeds along the route in Vermont to 59 miles per hour (95 km/h) between St. Albans and White River Junction, Vermont, and to 79 miles per hour (127 km/h) between White River Junction and Vernon, Vermont.
On October 5, 2012, the Federal Railroad Administration announced the completion of track work within the states of Vermont and New Hampshire for the above-mentioned stimulus plan. 190 miles (310 km) of track within the states of Vermont and New Hampshire were refurbished. The track work included installation of continuous welded rail, road-crossing improvements, ballast replacement, tie replacement, bridge repair and renovation, and embankment improvements. The top speed of the line within Vermont was increased to 79 miles per hour (127 km/h). The Massachusetts portion of the track work was ongoing as of 2015.
On October 5, 2015, the southbound Vermonter derailed in Northfield, Vermont after striking a rock slide. Five cars and the engine derailed; the engine and an empty car slid down an embankment. Five passengers and two crew members were injured, one seriously.
Until 1987, the Montrealer traveled on the Connecticut River Line between Springfield and Brattleboro with a stop in Northampton. Due to the deteriorating condition of the tracks in that section, Amtrak ceased service of the train.
When the Vermonter service restored train service between Springfield, Brattleboro and points north in 1995, the Vermonter traveled a somewhat indirect route east to Palmer, Massachusetts, and then up the east side of the Connecticut River via Amherst, Massachusetts. It used CSX Transportation's Boston Subdivision between Springfield and Palmer. At Palmer, it made a backup move on to the New England Central Railroad (NECR), as no direct track connection existed. Massachusetts rehabilitated the more direct Connecticut River Line route with $10 million in state and $73 million in federal American Recovery and Reinvestment Act funds.
During rehabilitation of the Connecticut River Line, Vermonter service was restored to it on December 29, 2014. With the re-route, the train ceased stopping at Amherst but a stop was restored to Northampton and, for the first time for Amtrak, a stop at Greenfield was added. The re-route and consequent elimination of the backup move is expected to eliminate about 25 minutes of travel time between Springfield and Brattleboro when the line rehabilitation is complete sometime in 2016.
In January 2015, the number of Vermonter riders using the two new stations (in Northampton and Greenfield) was up 84 percent compared to the equivalent station in Amherst the previous year.
A stop in Holyoke was added in August 2015.
Efforts have been underway for many years to extend the Vermonter to Montreal. In 2012 the Federal Railroad Administration awarded $7.9 million to allow for the upgrade of the existing freight rail line between St. Albans and the Canada–US border. Work on this project was completed in late 2014.
On March 16, 2015, the United States and Canada signed the "Agreement on Land, Rail, Marine, and Air Transport Preclearance Between the Government of the United States of America and the Government of Canada". The agreement would allow for the establishment of a preclearance customs and immigration facility within Central Station in Montreal that could be used by the Vermonter and Amtrak's Adirondack train.
Before the Vermonter can be extended to Montreal the Congress must pass enabling legislation for the preclearance agreement and the Parliament of Canada must ratify the agreement. Construction of a preclearance facility in Central Station is expected to take about three years; one year for planning and permitting and two years for construction. Construction of the preclearance facility is not expected to start until after the preclearance agreement has been approved by both governments. Enabling legislation was enacted by the United States on December 16, 2016 as the Promoting Travel, Commerce, and National Security Act of 2016.
The Massachusetts Department of Transportation and the Vermont Agency of Transportation are conducting a major study to "examine the opportunities and impacts of more frequent and higher speed intercity passenger rail service on two major rail corridors known as the Inland Route [the New Haven to Springfield route] and the Boston to Montreal Route."
The Boston to Montreal corridor being studied runs west from Boston to Springfield Union Station. From Springfield the rail corridor follows the route of the Vermonter northerly to St. Albans. From St. Albans the corridor continues to the Canada–US border and onward to Montreal Central Station in Quebec. The study is the precursor for possible increased passenger rail service on the route of the Vermonter north of Springfield.
The Vermonter uses Amtrak's Northeast Corridor and New Haven–Springfield Line between Washington, D.C., and Springfield, Massachusetts. It then uses the Massachusetts Department of Transportation (MassDOT)-owned Connecticut River Line between Springfield and Northfield, Massachusetts. North of Northfield it uses the New England Central Railroad.
A typical Vermonter currently consists of four Amfleet passenger cars and an Amfleet cafe car. Between New Haven and Washington the train is pulled by an Siemens ACS-64 electric locomotive (replacing the EMD AEM-7s that were retired in 2016). North of New Haven diesel GE P42DCs handles the train.
Prior to the 2014 reroute, the Vermonter operated with an Ex-Budd Metroliner cab-car, three Amfleet coaches, a Business Class/Cafe, and a P42; the consist reversed directions in Springfield, typically having the P42 leading north of Springfield and trailing south of Springfield. During winter periods the cab-car would be swapped for an Amfleet coach, and a P42 would be on either end.