Mercer County, you're off the hook.

For the last four decades, a 16-mile stretch of highways around Trenton constituted the last stretch of the East Coast's Interstate 95 that wasn't technically I-95.

But when massive steel beams went up over an existing stretch of I-95 in Bristol Township in mid-February, they symbolized an end to the Mercer County "missing link."

Now, on Friday, the Pennsylvania Turnpike announced those steel beams and the concrete roadway poured on top of them are opening to the public for use as early as this weekend, or, by the latest, the Monday morning commute Sept. 24.

“Motorists who travel in this area have been waiting a long time to realize the benefits this direct link will bring, namely reduced congestion on Bucks County roadways and improved traffic flow in the Philadelphia region and the entire east coast,” Turnpike Commissioner Pasquale T. "Pat" Deon Sr. said.

The overpasses, or flyovers as they are also called, are just north of Philadelphia and 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.

It’s the last piece to a highway more than 60 years in the making, first envisioned as a crucial part of the Eisenhower Interstate Highway System. And it’s the completion of a 1,900-mile road that finally links Maine to Miami seamlessly.

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

About 75,000 vehicles travel through that area on I-95 (around what used to be exit 40) each day, and another 50,000 travel the Pennsylvania Turnpike there.

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."

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 were able to scuttle the project.

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."

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 who did the work and provided the material and transported, for instance, those massive steel beams.

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