The end of the road to Gibson Island is where the mystery begins.

The signs dot Maryland Route 177, Mountain Road, in Anne Arundel County: "NOTICE. ROAD ENDS. NO OUTLET." Thick tangles of winterberry and spicebush soon give way to panoramic vistas of the Chesapeake Bay, and for most of us, the road does end.

For Gibson Island's 600 residents, the road home is just beginning. Their vehicles glide past the guard post and disappear on a causeway curving over water toward the cloistered and exclusive 2 1/2-by-1 1/4-mile island. Blustery breezes sweep the protected Magothy Narrows harbor to the north, where the boats of the Gibson Island Yacht Squadron ride silently at anchor.

It looks like heaven, and like heaven, you can't visit unless you live there.

Privately incorporated Gibson Island sits in the Chesapeake Bay 45 miles from the Capitol. It's one of the region's wealthiest places: It was ranked 14th on a Forbes magazine list of America's 150 priciest Zip codes, topping No. 15 Beverly Hills 90210 -- and far above any other Zip code in the region.

Outsiders generally aren't welcome, and many of the intensely private residents are reluctant to discuss their neighborhood.

Not all, though. "I've always felt that it doesn't hurt to talk about the island," said resident Charles W. "Pete" Shaeffer Jr. "Some people don't agree with that, but it takes a lot of the mystery out of it."

Still, Shaeffer admits, when asked where he lives, "We just say 'Down Mountain Road.' We don't say 'Gibson Island' because some people have a negative reaction to that. They view the community as being full of rich, pampered people. And I don't think that's an accurate characterization. I can tell you, these are mostly hardworking people."

Shaeffer, a resident since 1973, is a former president of Gibson Island Corp., essentially a small-town government with its own fire engine, specially commissioned police force and round-the-clock gate keepers. Seventy percent of the island is undeveloped hardwood forest owned by the corporation (each homeowner receives shares).

The island's startling natural beauty is preserved by the secluded placement of its 200 homes, which are nestled deeply in tall stands of oak and red maples and separated by misty swaths of marsh. On approach from the causeway, the effect is that of uninhabited wilderness.

Most of the houses sit bay-front on the island's east side, or at the south end, where Mountain Bar Point juts out like a horseshoe crab's tail. Residents delight in the point's white-sand beach. The homes at the island's south side are surrounded by 10 to 12 acres of grounds; most other lots are smaller.

And it's a bird sanctuary, so historically cats have been banned. The few that sneaked in are referred to -- with a wink -- as "Gibson Island squirrels."

"You can't get on the island unless you are an owner or are invited in by an owner," said Jeffrey Alexopulos of Coldwell Banker Residential Brokerage in Annapolis. "They are people who value their privacy and are willing to pay a premium price for great waterfront property."

Alexopulos said recent sales have included an estate for $5.2 million (complete with yearly tax bill of $17,092) and a replica of an Italian monastery for $3.675 million. Homes range from 1920s cottages to the French chateau with a 500-foot deck and 300-foot porch.

A tiny post office is the only speck of federal property, and nonresidents are, by law, permitted to use it. But be forewarned: Visitors asking at the gate to mail a letter are told not to wander from the path to the building and are usually followed.

In 1922, when Mountain Road was paved with oyster shells, Baltimore Judge W. Stuart Symington Jr. and others paid three farmers $165,000 for the island. Back then, many families of politicians and businessmen in Washington and Baltimore summered in Watch Hill, R.I., or Lake Winnipesaukee, N.H.

"And the husbands usually didn't see them," said Shaeffer, a stockbroker in Baltimore. "So the theory was that there would be a community close enough that everyone could go down on weekends and be with their families."

According to Shaeffer, the island's 1,000 acres were designed by the Olmsted brothers, landscape architects and sons of Frederick Law Olmsted, who laid out New York's Central Park. The Gibson Island Historical Society did not return telephone calls for comment or confirmation.

Gibson Island property values have appreciated "dramatically," Shaeffer pointed out. "It's nice . . . but the downside is that your taxes are following right behind. I'm paying 12 times what I paid in taxes in 1973. A lot of the older people can't afford it anymore."

There are no black homeowners on Gibson Island and very few other minorities. "But we have absolutely no prohibitions on that issue," Shaeffer stressed, adding that several Asian families have bought homes.

There are no retail stores, and kids must go off the island to attend public school. There are a boathouse, pool, golf course, tennis courts and a skeet range, all amenities of the Gibson Island Club, with membership subject to sponsorship and election. A community center is open to all residents.

The private Gibson Island Country School has about 100 students in pre-Kindergarten through fifth grade. Each summer, 70 island kids attend camp, where they are taught to sail, swim and play golf and tennis.

Despite the island's strong emphasis on privacy, it is still a neighborly place where people look out for each other, said Patty Cecil, an agent with Gibson Island Corp. Real Estate. She and her husband paid $80,000 in 1976 for their house on 44-acre Otter Pond.

The pond teems with largemouth bass and rockfish and is the largest freshwater lake on the Chesapeake Bay. Residents report shark sightings in the bay and playful northern river otter. "The first time I saw one, I thought it was a seal," Shaeffer said.

Crime and intruders are nonexistent. Unless one believes in the supernatural: In honor of Halloween, the Maryland Ghost & Spirit Association notes that Captain Kidd buried some treasure on Gibson Island.

Legend has it that, despite the bar on nonresidents, the old pirate's ghost has been spotted searching for his long-lost loot.

The island is ranked 14th on a Forbes magazine list of America's 150 priciest Zip codes, topping No. 15 Beverly Hills 90210.

Visitors to the privately incorporated island must be invited, and many residents don't want to talk about the place.