The massive steel beams went up over Interstate 95 just north of Philadelphia in mid-February without fanfare. Over two nights, workers completed an overpass that is still months from use.

But the connection is much more than a causeway of steel and concrete. It’s the last piece to a highway more than 60 years in the making. It’s the completion of a 1,900-mile road that finally links Maine to Miami seamlessly.

For decades, central New Jersey, specifically Mercer County, was the only remaining place on the East Coast where drivers traveling I-95 had to get off the highway for a short time. For the last four decades, building a link has been in planning.

"This is the last piece of that original system," says Jay Roth, an engineer with Jacobs Engineering who has been involved in the elusive connection for most of his long career. "It is meaningful to a number of people."

Come August, the overpass just north of Philadelphia will connect the New Jersey Turnpike to I-95 in Pennsylvania, ending the need to use Interstate 195 and Interstate 295 for 16 miles around Trenton.

About 75,000 vehicles travel through that area on I-95 (think the current exit 40) each day, and another 50,000 travel the Pennsylvania Turnpike there.

The frustration and confusion for many of those thousands of drivers will be assuaged by the new interchange, planners say. Not only will there be a smooth transition from the New Jersey Turnpike to I-95, there will also be the first-ever connection between I-95 and the Pennsylvania Turnpike.

Towns in the area will have to deal with far fewer vehicles exiting the highways, and swamping local streets.

All this translates into a big deal for the area's transportation system in an age when large-scale improvement projects have proven rare.

"Back in the '50s and '60s, a project like this happened every day," Roth said. "But with how built up the east side of the country is, (these days) we’re typically rebuilding. The accomplishment is that this is one of the big ones."

'Magic Motorways'

Norman Bel Geddes wowed people at the 1939 World’s Fair with an exhibit called "Futurama," which laid out a vision for American highways. By 1960, Geddes imagined, 14-lane superhighways would stretch across the United States and allow travelers to buzz along the roads at 100 miles per hour, according to Richard F. Weingroff, a longtime Federal Highway Administration official who has written about the agency's history.

Geddes put his thoughts into a book titled "Magic Motorways." The overall vision has yet to be accomplished. His trajectory for future events, much like Orwell’s "1984," was overly ambitious.

But the way Weingroff describes it in an essay for the FHWA, Geddes' proposals laid the foundation for President Eisenhower’s system — and, potentially, things that may yet come to be. Take self-driving cars. Geddes seemed to predict them to go hand-in-hand with those superhighways of the future.

"Radio beams in the cars regulated the spacing between them to ensure safety. In the cities, traffic moved on several levels — the lowest for service, such as pulling into parking lots, the highest for through traffic moving 80 km per hour," Weingroff writes. "Although the 'magic motorways' shown in Futurama were beyond the technological and financial means of the period, they helped popularize the concept of interstate highways."

In 1956, after a few years of legislative wrangling, Eisenhower signed the $25 billion Highway Act, which would finance construction of a 41,000-mile interstate system over the next 13 years. It was the largest public works project in the country’s history.

"This new highway program will affect our entire economic and social structure," New York master planner Robert Moses wrote in Harper’s magazine in 1956. "The appearance of the new arteries and their adjacent areas will leave a permanent imprint on our communities and people. They will constitute the framework within which we must live."

Opposition in 'Rustic' New Jersey

In the early 1980s, the first plan to close the I-95 hole in central New Jersey proposed a new highway through Mercer County, but opponents there proved a capable bunch.

The county executive at the time, Bill Mathesius, described the local feelings as "a specific revulsion to tearing up a rustic community — a rural community — and putting 95 through it."

"There would be fundamentally a six-lane highway going through this area, with off-exchanges in one or two places," Mathesius told National Public Radio. "Those places would have been developed."

Illustrating just how long the process has taken, NPR’s story quoting Mathesius, titled "At Last, I-95’s Missing Link Hits the Road," was published in August 2010.

Eight years later, the road is here.

It took some 35 years, spanning whole careers for many accomplished planners and engineers, to solve the Mercer County obstacle.

The plan now bypasses the central Jersey communities just east of the Delaware River, and uses long-held right-of-ways to connect the New Jersey Turnpike near exit 6 to Interstate 95 in Bristol, Bucks County.

This map illustrates the before-and-after designations. Click on the slider to see the differences.

The cost of such a project is monumental beyond the time it has taken. Then again, the $425 million in financial costs doesn’t truly capture the incredible coordination that goes into a federal highway project spanning two states. There is the Pennsylvania Turnpike Commission, which is overseeing the major components of the project. There are three Departments of Transportation involved. There is the numerous local communities involved. There are hundreds of contractors and vendors and suppliers doing the work and providing the material and transporting, for instance, those massive steel beams.

Consider one of the most mundane tasks associated with the project: changing the road signage. There are 2,000 signs that need to be swapped out and replaced.

The signage swaps are taking place in stages. Drivers along the soon-to-be extinct stretch of I-95 in Mercer County are already seeing new exit numbers and warnings that the road will soon become part of I-295.

Here's a look at the old signage versus what drivers will eventually see. Note how I-295 now goes all the way to Bristol where the new interchange has been constructed.

"It gives a magnitude of what we’re doing," Mark Raup, a project manager with the Pennsylvania Turnpike, said. "It's not like flipping a switch."

Last Piece of the Puzzle

The project is officially called the PA Turnpike/I-95 Interchange, which masks its symbolic and tangible accomplishments.

Sure, it's a highway infrastructure project, but it's also about decades-old missing links and visions of "magic motorways."

Brian X. McCrone/NBC10

Eisenhower would be happy to hear his vision of a more connected country is still playing out.

"The united forces of our communication and transportation systems are dynamic elements in the very name we bear — United States," he said in 1955. "Without them, we would be a mere alliance of many separate parts."

For Roth, it’s an example of American perseverance.

"It’s been talked about for so long," he said, adding that for many people over the years, "They didn’t think it would ever occur."