ALEXANDRIA BAY, N.Y. — Even the name of the Thousand Islands region in the St. Lawrence River between New York and Canada is an understatement.

Once a playground for the rich who built castles as monuments to themselves and their loved ones, the region is dotted by hundreds more islands than its name would tell.

Some say the number is more like 1,700, while Paul Malo, who has written extensively about the region, says the number is 1,860 "or thereabouts."

Others believe it depends on how islands are defined. "They generally have to have a tree on them," said Malo, a retired professor of architecture at Syracuse University in central New York.

Like oversized skipping stones, all manner of islands sprinkle the St. Lawrence River. The rocky upheavals covered by pine trees are large or small, some with sizable communities, others with no more than a tree and a house.

Some are home to striking castles dating to an era of conspicuous wealth, grand hotels or whimsical and Victorian-style homes.

Islands named Howe and Carleton, Grenadier and Bostwick, and even assemblages such as the Admiralty Group of 64 islands give visitors great views of the river and other islands and plenty of opportunities to hike or boat.

The islands also provide an obstacle course for endlessly moving river channels and passageways with names such as Fiddler's Elbow, Lover's Lane and Molly's Gut that eventually make their way to Lake Ontario.

The region has gone through many transformations. It was a draw for French fur trappers in the 17th century and served as a battleground during the War of 1812. That story is told at Sackets Harbor Battlefield, which was the center of U.S. naval operations on Lake Ontario.

Less than 100 years later, the Thousand Islands region became a destination for New York City residents who traveled by overnight train to nearby Clayton. "They'd go from a train to a yacht," Malo said.

The area was attractive to the wealthy during the Gilded Age following the Civil War when industry grew rapidly and financiers and industrialists became vastly rich. The Thousands Islands, due to its proximity to Canada, also was used by bootleggers during Prohibition.

The region now draws tourists to view the handiwork of the long-gone superrich. Visitors, for example, line up for a quick ferry ride to Heart Island and a tour of Boldt Castle, a spare-no-expense palace built at the turn of the 20th century by George Boldt. Boldt, the proprietor of the original Waldorf Hotel in New York, is credited for introducing elite hotels.

According to one local legend, Thousand Islands salad dressing was created by Boldt's steward while sailing on Boldt's yacht one day. The mayonnaise-based dressing has long been served at the Waldorf.

Boldt's six-story, 120-room Italian Renaissance-style manse includes tunnels, a powerhouse, Italian gardens and a drawbridge. The sudden death of Boldt's wife in 1904 prompted him to order a halt to construction, four years after work began.

Dark Island is home to Singer Castle, named for Singer Sewing Machine Co., the employer of Frederick Gilbert Bourne who built the estate for his family.

The 28-room castle includes a medieval entranceway with knights of armor standing guard beside a marble fireplace, a marble stairway, a walnut-paneled library with a secret panel connecting to passages in the walls and grates to spy on guests built into the walls.

Not all the homes are so grand. Many are modest dwellings that simply provided residents with easy waterfront access and natural beauty.

Thousand Island Park on Wellesley Island is known for its spacious clapboard homes, many with large front porches. The first generation of Americans to have second homes settled on Wellesley Island early in the 20th century and many homes have gone through preservation efforts, contributing to a renaissance of the park, Malo said.

Turreted homes and gingerbread-style cabins replaced Methodist campsites at Butternut Bay, one of several sites in the region organized as a religious camp in the 19th century.

Nature has provided its own shelter in the region's aquatic environment. Lush, grassy reed beds along shorelines protect pike, bass and carp while cattail marshes serve as nurseries for fish, waterfowl, reptiles and amphibians.

Public recreation places and nature preserves have been established in Canada and New York. The St. Lawrence Islands National Park includes 21 sites on more than 20 islands and in Canada. On the other side of the St. Lawrence River are 14 New York state parks, several on islands accessible to boaters, but most others that can be reached by car.

The Minna Anthony Common Nature Center, the largest nature center in the region, offers three miles of shoreline and a 600-acre preserve at the Wellesley Island State Park.

The nature center, which is accessible by car, includes a natural history museum, 8 miles of hiking and skiing trails and a canoe program.

Because of its distance from New York the region is not well-known, Malo said. But to residents and those who have spent decades of summers on the islands, the attraction to the region is no mystery.

"We think there's something special about it," he said.