MEXICO -- Pity the average gringo who ventures south of San Diego into that magnificent territory known as Baja California.

Eight hundred miles of desert, mountains, oases, untamed coastline and untold surprises lurk between the border and the arch rock at Cabo San Lucas. Baja California is the third-longest peninsula in the world, yet 90 percent or more of Americans never stray beyond Ensenada, an hour's drive south of the border. Or they fly straight to the dolled-up resorts of Los Cabos, jetting 35,000 feet above the empty terrain.

Perhaps it's just as well that most gringos never see what lies in between, the vast, nearly empty swath of land that comprises the vast majority of Baja California. Yet adventurous sorts have been coming here for many, many decades. They almost hunted the gray whales to extinction at Scammon's Lagoon back in the 1850s. John Steinbeck found them smuggling guns in 1940, and in the last three decades they've been coming in greater numbers. The modern era of travel in Baja started in December 1973, when workers completed the final mile of Mexico Highway 1. The 1060-mile highway linked the border with Cabo San Lucas for the first time, providing ready access to the towns and a myriad of attractions along the way.

HIGHWAY 1

Highway 1 did not "ruin" Baja, as some old hands at feared, entombed beneath a wave of condos, strip malls, marinas and southbound traffic. Baja has grown a lot, though most of that would have occurred with or without a new road. Sprawling new factories, high-rise apartment blocks, shopping malls and millions of migrants have transformed the border region, where Tijuana is now the fourth-largest city in Mexico. Seafront resorts, gaggles of timeshares and green fairways have turned the Los Cabos area into one of the country's leading tourist destinations.

In between, though, lie many hundreds of miles of land that travelers from el norte fondly call "the real Baja." It's a place of lonely ranchos, tiny fish camps, chalk-colored mesas and rugged sierra -- where cartoonish-like buzzards glare down from gnarled cacti and bovine skulls lie half-buried in sand. Gringos may always argue about where the "real Baja" begins, just as they come here for all sorts of reasons. There's no way to list them all, but I can list some of the main subgroups coming to Baja.

GRINGO CHECKLIST

Off-Road Warriors: This is not an easy group to categorize. On the one hand, there's the Baja 1000 set, who've been coming here in increasing numbers since the 1960s. They surely appreciate Baja's beauty and tranquility, and have plenty of friends and supporters up and down the peninsula, Still, they don't do much to enhance it with their high-horsepower machines tearing across the desert. On the other hand, you have the dedicated explorers in their well-worn Jeep Wranglers, Ford Broncos and early-vintage Toyota Land Cruisers. You'll find them in remote places like Bahia Tortugas, San Francisquito, San Javier, and Bahia San Luis Gonzaga -- dozens of bone-jarring miles from the nearest paved road.

The RV Set: They come from all over the west -- "snowbirds" fleeing the snowdrifts of Montana and Alberta or leaden skies of the Pacific Northwest. Either way, it's a large enough group that it's impossible to overlook, as you'll discover while driving down Highway 1 between late fall and early spring. Some go it alone, while others travel in caravans of 20 or 30 vehicles -- traditional campers, house trailers, fifth wheels, motor homes the size of a Greyhound bus. You'll see them lining the shores of Bahia Concepcion, in full-service RV parks in Cabo, or at countless seaside camps along the gulf south of San Felipe. Most measure their stays in weeks or months.

Nature Explorers: I could break this group into a hundred subgroups, but collectively they come closest to the classic definition of "eco-tourists." For many years now, outdoor-sport journalists have enthralled us with tales of their pursuits: divers riding the backs of whale sharks in the depths off Cabo, kayakers exploring the turquoise waters of Bahia de los Angeles, grownups bursting into tears after stroking a gray whale on the head in Scammon's Lagoon. For nature aficionados, Baja is a verifiable nirvana -- a land of untamed deserts, hidden oases, arid and verdant mountains, corralled by nearly 2,000 miles of breathtaking coastline -- all this with barely a half-million people between Ensenada and Cabo San Lucas.

Extreme Athletes: Well, "extreme" may be a reach, but the point is that many outdoor types set their sites hundreds of miles south of the border in their quest for something new and different. They include surfers heading for "secret spots,"cyclists peddling the length of Highway 1, windsurfers riding wintertime's blasts at Los Barriles. Like their nature-exploring brethren, they're fleeing the maddening crowds of the Golden State, and the sheer remoteness of Baja is irresistible -- the prospect of going somewhere none of your friends have been or are likely to go to.

Sport Anglers: I hate to single out just one sport, but anglers from California were plying the prolific waters off Baja decades before Highway 1 blazed a path to Cabo, and they're still at it today. Jousting a marlin or sailfish off the stern of a nice-sized cruiser out of in the Sea of Cortez remains one of the peninsula's classic images, but fishing in Baja goes far beyond that. Odds are you'll rent an open-air motor launch known as a panga in their quest for tuna, dorado, yellowtail and other mid-sized game fish in the seas off La Paz, Loreto, Los Barriles or Los Cabos. Others join long-range charter boats out of San Diego that work the waters off San Quintin, Isla Cedros, Bahia Magdalena and elsewhere along the Pacific coast. Still others book charter trips out of San Felipe that head for the nutrient-rich waters off Bahia de los Angeles.

Retirees: It's one of Mexico's worst-kept secrets -- that this country is one great place for Americans to retire, and Baja California is no exception. Californians in particular set their sites on Baja, and depending on whom you talk to, up to 30,000 have set up housekeeping in the Rosarito-Ensenada area alone. Many more have settled in San Felipe, Mulege, La Paz and the Cape Region. Regardless of venue, their pension checks go a lot further down here, and those with modest tastes can live comfortably on $1000 a month, maid service included. Plus, the locals are friendly, the climate is muy agradable (at least during winter), and E-mail and satellite TV keep them in touch with the world up north.

Urban Refugees: They got fed up with L.A. gridlock, keeping up with the Joneses, wearing a tie 9 to 5 and the rest of the rat race regimen ... and did something about it. Most build new lives near the border or down around Los Cabos, but you'll catch them all over in between -- running hotels in Mulege or Bahia de los Angeles, selling real estate in Los Barriles or San Felipe, selling their paintings in Todos Santos, leading sport fishing trips out of La Paz. If there were a tagline to hang on this group, it would have to be "no bad days."

EXCEPTIONS TO THE RULE

This list is by no means exhaustive, and many more Alta Californios head to Baja for all sorts of reason or no reason at all. Take the middle-aged couple from Bakersfield I met up with in San Quintin, who decided on a whim to jump in their Lincoln Town Car and make the long drive to Cabo and back. They were on their way home, after having the time of their lives. Or how about the parish priest at Mission San Ignacio who once had the choice between two assignments -- one in downtown L.A., the other in Baja. He made his pick 40 years ago and never looked back. Then there were the two-dozen or so squatters who had taken over a seaside plot near Cabo Pulmo on Baja's East Cape. Quintessential beach bums, they were having their fill of fresh seafood, chugging cervezas and playing bocce ball while perfecting their bronzed hides beneath the midwinter sun until the landowner kicked them out.

Fortunately, your author has found that last group is a distinct minority -- since most Californians and other extranjeros who visit the "real Baja" revere and respect their surroundings while living productive, responsible lives. It is those who accept the land on its own terms and wish not to bend it too much to their own will who may be the best hope for preserving one of the largest, and most inspiring frontiers in the world.