A region divided by a white curtain

Instead of piling into an SUV to visit grandparents on the opposite slope of the mountains, each member of the clan climbs aboard a snowmobile.

As they have every Christmas and most Thanksgivings for a dozen years, the kids follow Dad up the snow-crusted state Route 4, over the icy crest of Ebbetts Pass and down to Grandma's house for turkey dinner.

Practicality, not adventure, prompts these and other wind-whipped treks. Snow closes Route 4 to cars all winter. The alternative route to the Sierra's far side is a circuitous seven-hour round trip through four counties. A snowmobile cuts the journey to less than an hour each way.

Rick Stephens, a no-nonsense Alpine County sheriff's sergeant with a walrus mustache, shrugs as if it's no big deal. Such is life in California's cleaved counties.

Even in the most placid season, the state's highest ridgeline looms as an obstacle to civilization's spread. Big winters like this year's turn that physical division into a brick wall, a seasonal shutdown that shapes life in ways big and insignificant.

In lofty Alpine County, where 9,000-foot peaks capped by abundant snow fit the region's name, package delivery firms won't guarantee overnight delivery from one side of the county to the other, though it's barely 20 miles as the crow flies.

Courts in Markleeville, the county seat, don't bother with winter jury duty for residents who can be marooned on the wrong slope. A county building official once drove 15 hours through two snowstorms to inspect a new foundation.

Randy Gibson, Alpine's longtime building chief, endured that arduous trip in the winter of 2003. He said it was not so much a hassle as "just another day in paradise."

The disruption hits in the six counties that straddle the Sierra to the north and south of Lake Tahoe: Alpine, El Dorado, Placer, Nevada, Sierra and Plumas. Each came into being shortly after the Gold Rush, their boundaries drawn to suit the need for towns and mineral assay offices close to the mines.

Nancy Thornburg, a longtime Alpine County resident, says the county lines spring from an early mistake, the drawing of the state boundary east of the Sierra.

Folks on the Sierra's east side may live in California, but they shop and send their kids to school in Nevada. They watch Nevada TV stations. They keep abreast of Nevada politics.

"Some idiot way back when drew the state boundary at the wildflower line on the east side instead of where it should have been, up on the summit," Thornburg said. "If they'd done it right to start with, we'd be part of Nevada and everyone would be happy."

In some spots, the cultural divide is deeper than the snowdrifts.

Consider that Sierra County's annual Kit and Caboodle fair on the east side rarely attracts anyone from west slope towns. Vice versa for the west side's annual mountain bike festival.

"They've got their little world over there, and we've got ours," said Brooks Mitchell, a county supervisor. "It's basically been that way for about 150 years."

As brutal as winter driving conditions get in Mitchell's neck of the woods, travel is tougher to the south, as the Sierra peaks rise ever higher. Interstate 80, the bustling highway into Lake Tahoe's north shore, tops out a tad higher than 7,000 feet, but farther south, the elevation of Ebbetts Pass is more than 8,700 feet, Sonora Pass reaches 9,600 feet and Yosemite National Park's Tioga Pass is nearly 10,000 feet.

The California Department of Transportation shuts down the three passes each winter, padlocking metal gates at the foot of the highway ascent on each side of the Sierra, sometimes for more than half the year.

Residents greet it as a part of life. And adapt.

"The barrier is as much psychological as it is physical," said Eric Jung, a real estate agent in Bear Valley, located amid the conifers on the Sierra's west slope.

Jung knows every bend in the road, battling long winter drives during four terms on the Alpine County Board of Supervisors. The lovely journey of 40 miles over Ebbetts Pass in the summer swells to nearly 160 miles on the circuitous winter route. There is no snowmobiling for him: "I have to have my heated cocoon with my CD player."

Rick Stephens, the Alpine County sheriff's sergeant, has lived on both sides of the divide. He grew up in Markleeville, where his dad ran the towing service. But a love of snowmobile racing led him as an adult to Bear Valley, where the entire community - adults going to work, kids heading to school - gets around on the motorized sleds.

He gave up racing a few years ago to serve as pit chief for his son, 20-year-old Luke, a racer last seen on TV at the Winter X-Games. Dad still gets plenty of time on a snowmobile patrolling the town's snow-decked streets. Stephens and his two deputies also make runs up Route 4 on weekends, rescuing busted-up snowboarders and stranded tourists.

"It's faster on a snowmobile in winter than driving the road in summer," he said, noting how the highway narrows to a single lane in some spots and makes maddening switchbacks. His record through the snow: 22 minutes gate to gate.

One recent afternoon found Stephens and Deputy Jeff Stanford whizzing up the road. Luke Stephens tagged along for the trip, occasionally snaking into the winter wilds to whiz up peaks and fly off jumps.

Over the gourse of a couple of hours, they stopped to check on a three-legged bear wintering in a bathroom near the snowed-in Hermit Valley rest stop and later offered help to a broken-down snowmobiler from Sweden.

Near Ebbetts Pass, another snowmobiler slowed to greet them. It was Sheriff John Crawford. The sheriff handed over some department documents and chewed the fat with Stephens. "I ride over seven or eight times a winter," said Crawford, whose department has almost as many snowmobiles (nine) as sworn deputies (13).

Crawford's worst trip was the day spent struggling through thick snow to reach the summit. But days like this make up for it, he said, gazing through sunglasses to where the summit and sky collide.

"It sure beats driving."