CARIBOU, Maine - For 50 years, the people of northernmost Maine have waited in vain for a proper north-south highway, a sleek black ribbon to stitch the state’s remotest farms and forests to the rushing interstate that ends 100 miles south.

Now, to the surprise of many here, the dream has been revived, and a first small segment of the highway is slated to be built next year.

The north-south highway in its vast entirety - some 130 miles of road, projected to cost $500 million to $1 billion - is almost impossibly ambitious. But in recent months, Maine legislators and officials have taken steps toward beginning its construction, breaking off a handful of more manageable segments and finalizing plans to build an initial, 3-mile section, a $20 million bypass around Caribou’s downtown, beginning next spring.

The tentative steps have stoked fresh hope in Maine’s farm country, where two-lane Route 1 meanders between endless patchwork fields of potatoes and broccoli. But it has also rekindled old tensions between the state’s less prosperous northern fringes, where residents have complained for generations of being misunderstood and forgotten, and its booming southern portion, where some see the north as an economic burden.

“Most of the population is in southern Maine, and they do well in good times, and the argument is made that we are a drag on them,’’ said Troy Jackson, a logger and state senator from Allagash, in northern Maine. “We’re trying to do something about that.’’

Advocates for the highway say it would revitalize commerce in the region, cutting travel times to make it more appealing to businesses and tourists. A seven-hour drive separates Maine’s southern border from the northernmost fringes of Aroostook County, an enormous swath of woods and farmland where the verdant St. John Valley hugs the Canadian border.

Interstate 95 ends in Houlton, near the county’s southeastern corner, two to three hours south of the towns on its far northern rim. Without a highway, people and businesses there must rely on smaller roads, on which speed limits ratchet up and down as they pass through towns and villages.

On Route 1 north of Houlton, 18-wheelers toting heavy loads of timber and potatoes from the northern fields and forests roar through busy downtown Caribou and Presque Isle, stopping at red lights.

“Transportation is one of the key assets a community can have,’’ said Walt Elish, president of the Aroostook Partnership for Progress, whose hilltop office, in a converted Caribou farmhouse, overlooks miles of emerald fields. “Anything that decreases the time it takes to get goods to market helps keep the area attractive.’’

The highway plan that recently emerged is much more modest than the original vision, which would have laid long stretches of fresh pavement through the woods. For much of the way north, the latest initiative would simply improve existing north-south roads, including Route 1, leaving them two lanes, but acquiring the property to add new lanes in the future if needed, and adding time-saving bypasses around towns and cities.

Whatever its path, such a road would ease bitterness that has lingered since the interstate was built. When the state started building the Maine Turnpike, in the 1940s, plans showed a road stretching to the St. John Valley. But in the 1950s, when the federal government allocated money for the interstate system, new plans routed the highway to Houlton, where the government deemed the road complete.

“It led to a feeling of being left at the altar,’’ said John Melrose, a former state transportation commissioner who now advises economic development leaders in northern Maine. “There is a level of anger in the region that they were left and forgotten and a feeling they deserve the same as everyone else.’’

Years of job losses in the region nurtured those feelings, and this spring, emboldened by the recent flow of federal stimulus money, Jackson filed legislation asking for funds to build the long-deferred highway. Some southern Maine legislators attacked his plan, saying it would consume too much money, benefit too few people, and stall smaller road projects in their districts. Their resistance was not unexpected. But in April, a headline in the Kennebec Journal, in the state capital of Augusta, reopened old wounds when it called the proposed highway a “road to nowhere.’’

The paper printed an apology, but northerners were stung. Fierce, emotional debate erupted. A pair of former state legislators from Frenchville, Ross and Judy Paradis, declared in an outraged letter to the editor that the headline writer should be fired “to promote justice and equality for all the citizens of Maine.’’

In the Legislature, the bid for stimulus money failed. But lawmakers passed compromise legislation, seen as another significant step forward for the project, directing state transportation officials to make it a priority and seek other funding for it.

The project already has cash in the bank. Some $50 million in federal highway funds, appropriated for the north-south highway in the last decade with support from US Senator Susan M. Collins, sat idle while the project languished. About $40 million remains, after spending on feasibility studies, half of which will be used to build the Caribou bypass.

“As a native of Aroostook County, I understand that the North-South highway is critical for the future economic development of Northern Maine,’’ Collins, a Caribou native, said in a statement last week. “The planning, design and construction of the Caribou Connector are important first steps.’’

John Dionne, a retired businessman who grew up speaking French in Grand Isle, has spent much of his life fighting for the highway, convinced it could revitalize his beloved valley.

Heartened by the latest steps but cautious after years of disappointments, Dionne said he has never stopped believing that the highway will be built.

“It’s never too late,’’ he said.