As a provincial portion of the Trans-Canada, the highway's western terminus is at the interprovincial boundary with Quebec 15 km north of Edmundston.

It was one of the initial routes defined in 1927,[3] running from Quebec as a continuation of Quebec Route 2 via Edmundston, Grand Falls, Woodstock, Fredericton, Saint John and Moncton, After a short crossing of the New Brunswick Panhandle alongside the Madawaska River to Edmundston, Route 2 closely followed the Saint John River all the way to Saint John, crossing three times - from the east to the west at Grand Falls, back to the east at Perth-Andover, and back to the west at Hartland (on the Hartland Covered Bridge).

At Fredericton a controlled-access 4-lane section was built around the city, and the highway crossed the Saint John River on the Princess Margaret Bridge to the east bank just south of the central business district.

Following the river's east bank just metres above its water level (frequently flooded in spring freshets), the route continued south to Jemseg where the highway turned east along the southeast shore of Grand Lake to Youngs Cove Road where the highway turned south to Coles Island and on to Sussex.

East of Salisbury, Route 2 followed local roads over a series of low hills north of Moncton, cresting at Lutes Mountain, before descending and following a controlled access section bypassing the city and Dieppe, skirting the edge of the Memramcook River valley and on to Sackville, then Aulac, and finally the N.B.-N.S.

[citation needed] The provincial government changed in 1987 with the election of Premier Frank McKenna who was focused on improving the province's business climate.

Intensive lobbying from other provincial governments in the Atlantic provinces, as well as various trucking companies and business and transportation interests, asked that Route 2 be further upgraded.

As a result, the final years of the McKenna administration saw a significant realignment of Route 2 proposed, running from Longs Creek, west of Fredericton, bypassing it and Oromocto to the west, and continuing southeast to Jemseg, where it would cross the Saint John River and connect with an existing four-lane section south of Grand Lake.

225 km (140 mi) of new, four-lane, controlled-access expressway would be privately financed and built, with the builder charging tolls for a 25-year period before the provincial government would gain control of the highway.

In the late 1990s, an agreement was signed with a private consortium called Maritime Road Development Corporation (led by former provincial Liberal leader and former federal Minister of Transport Douglas Young) to build the new Route 2 alignment at an estimated cost of $1 billion (CAD).

The re-alignment and construction of Route 2 between Longs Creek and River Glade catapulted New Brunswick highways forward by decades virtually overnight.

The road was designed with 150 m (500 ft) medians, extensive wildlife fencing and underpasses, rumble strips along emergency breakdown lanes, paved emergency U-turn areas, sensors beneath the asphalt for monitoring truck weights as well as local weather and road surface conditions, extensive guard rails and reflectors, as well as two major bridges: the Saint John River High Level Crossing and the nearby Jemseg River Bridge.

The high quality of construction of the new Route 2 alignment and improvement in the provincial highway system was not unnoticed by the new government of premier Bernard Lord.

During this same period, negotiations were undertaken with the federal government to secure funding to complete the last, and one of the most costly parts of the new construction—a 98 km (61 mi) gap between Woodstock and Grand Falls over the Appalachian Mountains (bypassing present-day Routes 165, 103 and 130), and a 30 km (19 mi) gap between Longs Creek and Pokiok (bypassing present-day Route 102), west of Fredericton.

In August, 2003 a joint announcement was made by Premier Lord and Prime Minister Jean Chrétien for a $400 million (CAD) agreement to complete upgrades to the last remaining non-controlled access section of Route 2.

This construction saw a completely new alignment built north of Woodstock, staying several kilometres inland from the Saint John River's west bank, and paralleling the Canada–United States border north to Grand Falls, where it crosses to the east bank of the river and connects with existing four-lane upgrades to Route 2 through to the Quebec boundary.