Where, precisely, is the boundary between Northern and Southern California?

I've long wondered.

As a kid growing up in Orange County in the 1950s and '60s, I regularly drove north with my family to visit relatives in Marin County, across the Golden Gate Bridge from San Francisco.

We always arose early in the morning to begin our 400-mile trek, and were on the road by 4 a.m. We took U.S. Route 99 — once referred to as California's "Main Street" — straight up the state's Central Valley. We'd routinely stop for lunch at Modesto's A&W drive-in, which later gained acclaim in George Lucas' film, "American Graffiti."

We then made a hard left at Manteca and cruised into the Bay Area.

The 5 Freeway largely replaced the 99 in 1972.

After passing through Bakersfield on our way north — usually about 7 a.m. — I intuitively figured that we'd just crossed an invisible barrier into Lotus Land. It was a feeling difficult to describe.

Bakersfield itself — home of the Bakersfield Dodgers of the California League — was decidedly SoCal all the way. But above Bakersfield stretched a vast and intoxicating Northern landscape.

My gut was spot on.

There wasn't a tangible marker or checkpoint to announce our arrival in a strange and different country. Nor was it like what I experienced 10 years later when I entered Bizarro World, or the DMZ, a notorious and perilous boundary separating the two Koreas.

But I sensed upon entering NorCal that the air was different, the climate different and the culture different. We weren't behind "The Orange Curtain" any longer, Toto! Where else could you stumble upon "tangerine trees and marmalade skies?"

Northern and Southern California are obviously not sovereign geographic entities, but two different brands of the same soy milk.

California's Mason-Dixon traverses the northern limits of three abutting SoCal counties: San Luis Obispo, Kern and San Bernardino, north of the Tehachapi range. The counties' northern boundaries form a straight line running from San Simeon on the coast to Delano in the Central Valley to Ridgecrest nestled near the eastern mountains.

Throughout my life I've heard rumblings of an imminent breakup of the Golden State. Potential borders have been postulated all over the place, but so far it's been no more than sound and fury.

Which brings me to another fascinating North-South rift.

My wife Hedy and I recently returned from a visit with our daughter, her husband, and our four grandkids in North Carolina.

It seems that North Carolina has for decades been engaged in a discomfiting border dispute with its little sister, South Carolina. These former stalwarts of the Old Confederacy have been haggling since 1994 over their shared 334-mile frontier.

The original border dates back to the 1700s. The last full survey of the border took place more than 200 years ago. During that inspection, surveyors marked the official line by carving notches into trees –- a primitive procedure by today's GPS-influenced standards.

As a consequence, a special Carolinas boundary commission has for years been hashing out border discrepancies using the latest 21st century technology. The project is scheduled for completion in early 2013.

In retracing the original 18th century demarcation line and reviewing aged documents, the commission has determined that the border has been incorrectly marked — sometimes by hundreds of feet — in numerous locations.

As surveying has proceeded in recent years, many border residents who thought they lived in South Carolina have been disabused of that notion and told they reside in North Carolina. They're Tar Heels, not Gamecocks!

Some parents have learned that their children have been enrolled in the wrong school districts. Others have paid fees to the wrong utility companies.

Some face liability for back taxes, while others are eligible for refunds. It's all very thorny. By contrast, California's North-South brouhaha is far less prickly.

Residents of Waxhaw, NC/SC aren't certain which license plate to affix to their pickup trucks.

That's never been the case in Bakersfield.

JIM CARNETT lives in Costa Mesa. His column runs Wednesdays.