(MONEY Magazine) – Out in the Southwest, near the spot where U.S. Highway 160 crosses the San Juan River, there's a large, official-looking concrete slab carrying the official state seals of Utah, Colorado, New Mexico and Arizona.

This is the Four Corners, the only point in America where four state borders intersect and, therefore, a good place for pondering the nature of boundary lines. Although state, county and town borders are often dictated by relatively obvious guideposts like rivers, the Continental Divide or--as in the case of the borders that form the Four Corners--lines of latitude and longitude, they just as frequently seem completely arbitrary, as if a long-ago surveyor had said to himself, "A few miles east, a few miles west--who cares? Let's just put the damn line here."

While the Four Corners are hard to miss (thanks in part to all the tourists who insist upon splaying themselves on the slab and shouting, "Get the camera, I'm in four states at once!"), most of America's state border crossings are less conspicuous, less celebrated. Many of the towns abutting these borders, however, while not traditional tourist attractions like the Four Corners, hold a subtle but unmistakable interest all their own--towns where simply walking a few yards this way or that can put you in another congressional district, area code or even time zone.

One such place is State Line City, Ind., a tiny village on the Indiana/Illinois border, about 100 miles south of Chicago. The town is home to about 250 people, one retail enterprise (a corner store called the Country Pantry) and a marker designating the site of a short, rather uninspired speech given by Abraham Lincoln in 1861. A plaque carries the entire 75-word transcription, which suggests that the Great Emancipator hadn't yet honed the speechifying skills that he would later exhibit at Gettysburg ("Gentlemen, I shall address you at greater length at Indianapolis," reads a pivotal passage, "but not much greater").

State Line City, in other words, appears to be a thoroughly unremarkable place--until you encounter State Line Road, a thoroughfare that is the state line. People living on the east side of the street are in Indiana; those on the west side are in Illinois (and are technically residents of Bismarck, an Illinois town about 10 miles away, even though they're part of the State Line City community). And since the state border is also the dividing line between the eastern and central time zones, the two sides of the street are an hour apart--except during daylight saving time, which isn't observed in this part of Indiana.

Strolling along State Line Road is a surreal experience. On the one hand, the bucolic homes couldn't look more normal, and the only visible distinction between the two sides of the street is a slight difference in the typefaces used on street signs. But the road packs a considerable conceptual punch, with thoughts like, "Hmm, so that's Illinois over there" or "What the hell, I think I'll walk over to Indiana now" inevitably coming to mind. It's tempting to stand in the middle of the avenue and get run down by traffic, just to see which state the ambulance would come from.

If State Line City's pleasures are largely notional, things get much more tangible in Hurley, Wis., a border town nestled against Michigan's Upper Peninsula. I encountered Hurley after road-tripping for several days through northern Michigan, where I'd noticed a phenomenon I couldn't recall seeing anywhere else: Almost none of the Michigan bars had neon beer signs in their windows, except for an occasional O'Doul's sign. It was sort of sad--I mean, seriously, who's going to be enticed into a bar by a sign touting nonalcoholic beer?

Eventually I made my way to the state line and crossed over into Hurley, where I quickly noted that the town, despite a population of only 1,800, has more than a dozen bars within a three-block strip, all positively ablaze with neon beer signage. I set up shop at a joint called the Alaska House and quickly made friends with the bartender. "Nice-looking bars in this town," I said. "How come the ones over in Michigan don't have neon signs like the ones you've got here?"

"That's the law in Michigan," he explained, shaking his head in bewilderment as if it were the craziest thing he'd ever heard. "Can't have illuminated beer signs, unless it's nonalcoholic beer. That's why we've got so many bars in Hurley--everyone knows there's better drinking here in Wisconsin than in Michigan." So Hurley, much like the gambling municipalities perched just inside the Nevada state line, capitalizes on its border status by offering an essential service that's unavailable on the other side of the boundary.

Sometimes, however, what makes a border town interesting is simply the marking of the border itself. We've all driven across a state line on the freeway and passed a sign welcoming us to "Kentucky, the Bluegrass State" or "Wyoming, Like No Place on Earth." But what if a road crossing a border is too piddling to merit a big, flashy sign?

That's the situation in Hale Eddy, an upstate New York hamlet that sits against the northeastern tip of Pennsylvania. Faulkner Road, a sleepy little dirt artery winding through the southern part of town, crosses the state line with so little fanfare that it's easy to miss the border altogether. But off to the side of the road, at the edge of the surrounding forest, is a stone obelisk marking the boundary. Erected in 1884, it stands about six feet high and carries the names of both states' commissioners at the time.

The handsome, understated obelisk is much more appealing than the signs marking most highway border crossings and is definitely worth a stop. As I examined it myself last summer, the marker's century-plus longevity exuded a palpable air of history--a potent reminder that while boundary lines may not be visible, they're nonetheless very real. Best of all, I thought to myself, this marker, tucked away on an obscure backwoods road, will never be overrun with chucklehead tourists like the ones at the Four Corners.

Paul Lukas, winner of a Lowell Thomas Award from the Society of American Travel Writers, grew up in a small Long Island village, about 50 yards from the town line.