A multi-million pound bypass that has been 70 years in the planning officially opened in Powys on Thursday.
One haulier said Newtown bypass will make a "big difference" due to 45-minute hold-ups in the town, while the local AM said it was a "momentous" day.
The Welsh Government said the road will ease congestion by about 40% in the town centre.
A public notice printed in 1949 shows a bypass was being considered by the former Montgomeryshire County Council.
The four-mile (6.4km) road runs to the south of the town with two lanes in one direction and one in the opposite direction, to provide overtaking points.
For many in the area, it is hugely important.
Colin Owen, who runs RA Owen and Sons coal and agricultural merchants in nearby Llandinam, said Newtown has been referred to as the "car park of mid Wales" due to the length of traffic delays.
"People were afraid to go into town because they didn't want to go out of the traffic queue, because they'd only have to rejoin it again," he said.
"It is going to make a very big difference, and it will ease the movement of traffic and save us a lot of time coming through Newtown."
Life-long resident Joy Hamer, 86, who lived on the main road for many years, said traffic issues had long been a big part of local life.
"It will be a big thing for the town," she added.
Newtown mayor Sue Newham said: "A new chapter has begun for our town and we intend to make the most of every opportunity."
And town council clerk Ed Humphreys said: "Change is the lifeblood of opportunity for Newtown."
The bypass is opening less than three years after work started on the £95m project. But it has been a long road.
Why the hold-up?
A council public notice published in August 1949 sought "school boys 16 years of age or over" to work as enumerators to count vehicles for a traffic survey.
There were also discussions about a bypass in the 1960s and the 1980s but the green light never came, as many had mixed reaction to the idea.
In recent years, congestion around the town worsened, a situation that was blamed largely on traffic lights replacing a roundabout.
Increasing congestion led to a change in public opinion, according to Montgomeryshire Conservative AM Russell George.
The Welsh Government said the industrial development of Newtown had been "hampered by congestion issues".
Then, in 2008, it confirmed it would finance the project, and work was set to start in 2011.
But it was put on hold after a spending review in 2010.
'Improved air quality'
In 2011 a 10,000-name petition was presented to ministers by Mr George calling for work to start.
AM Mr George said the bypass opening was a "momentous occasion".
Nick Cleary, project manager for contractors Alun Griffiths, said the scale of the project had been a challenge, building four underpasses, three bridges and importing 350,000 tonnes of stone.
"This is one of the largest road projects for mid Wales," he said.
The launch was conducted by transport and economy minister Ken Skates who said it would "lead to shorter journey times and improved air quality in the area".