It may be surprising that President Dwight Eisenhower’s dream of a linked network of American autobahns is still (a little) incomplete in 2018, more than half a century after the passage of the Federal-Aid Highway Act. But the reason has less to do with recent national politics and much more to do with long-term planning, wealthy homeowners, the 1970s fuel crisis—and that pesky gap in New Jersey.

I-95 is an American marvel. It’s the longest north-south highway in the United States and the country’s most-used highway in terms of vehicle miles traveled, according to the Department of Transportation.

It’s efficient, serving about 10 percent of America’s land area but almost 40 percent of its population, or roughly 110 million people. Its path is “as densely settled as much of Western Europe,” brags the I-95 Corridor Coalition, a group of government agencies that maintain the route.

On the way, it passes an atlas of magnificent American town names: Jupiter, Mims, Pooler, Walpole, Applegarth, Throgs Neck, Mystic, and Gray—not to mention the novelty of New Zion, New London, New Castle, New Smyrna Beach, and New Limerick.

Yet despite all these accolades, I-95 isn’t particularly beloved or extolled—though it appears in at least one Springsteen song. In some ways, it’s a lot like the densest cities on its path: a little rough around the edges, and nothing special to look at, but every day it does its job without much of a fuss.

Except, that is, in New Jersey, where at one crucial juncture, I-95 utterly fails to work.

If you are driving northbound on I-95, just outside of Princeton, a road sign will warn you that I-95 North—the road you are on—is ending. But the physical road itself doesn’t end—instead, the highway veers south, now under the name Interstate 295. If you don’t get off at an exit, you will find yourself suddenly driving south, and have to do a complicated series of maneuvers to get back on a northbound road.

On the other side of this gap, Interstate 95 continues northward, starting from eight miles away.

It all sounds confusing, and it is—I didn’t fully understand what was happening until I reported this story, and I grew up 10 minutes from this stretch of interstate.

But while the current situation may be perplexing, the root cause of the problem is easy to explain: There was supposed to be a chunk of highway in this part of New Jersey, and no one ever built it.

Its origins go back to the late 1930s, when federal planners first proposed the idea of a national superhighway system. The authors of Toll Roads and Free Roads, a 1939 federal report that proposed interregional highways, envisioned a major north-south artery through central New Jersey. In 1955, Eisenhower adopted many of their plans when he first proposed the interstate system to Congress. He, too, slotted a highway into the same part of the state.

During the late ’50s, the new highway also got a name. State transportation officials agreed to christen the major interstates using the same scheme they used for the U.S. routes decades earlier: East-west highways would receive even numbers, while north-south highways would be odd. But U.S. routes started counting from the northeast, so to avoid confusion, the officials numbered interstates starting in the southwest. Thus, Interstate 95 runs north-south on the Atlantic Seaboard, roughly mirroring the old U.S. Route 1. (This is also why I-5 mirrors U.S. 101 along the Pacific.)