Whether they were sailing, fighting, or farming, people have always needed to know which way the wind blows.

But weather vanes have been used for far more than just a forecast.

A vane on a house or barn might show what business you were in, whether you lived in the country or along the seacoast, or simply what took your fancy. Great paths to self-expression, the objects would telegraph to all what was important to you.

One of the earliest American vanes still in existence - in the permanent collection of the Philadelphia History Museum - is a decorative iron banner with the initials of William Penn, two of his partners, and the date 1699. The vane, which topped a mill in Upland, was a business statement combined with a work of art.

While other categories of antiques have come and gone, weather vanes - and the prices they bring - have remained strong because buyers still use them as a form of personal expression. For weather vane collectors, the possibilities are almost infinite.

At a new exhibition of antique American weather vanes starting Saturday at the Brandywine River Museum in Chadds Ford, visitors can view a sea monster, an Indian with bow and arrow, and a celebrity horse named St. Julien who was "king of the trotters." The opening coincides with the museum's 42d Annual Antiques Show, where many of the 31 dealers will offer old weather vanes for sale.

New exhibitor Dennis Raleigh from Wiscasset, Maine, has been saving some of his best items for the show, including a very large cow, a fish, and a rare sheep weather vane from the folk-art collection of singer Andy Williams.

Vanes have long been considered American folk art. Some, cut from sheet iron by farmers, are truly folkie, with a hint of abstract expressionism. Others, ordered from New England factories, were made with molds created by talented sculptors.

Assistant curator Amanda C. Burdan, who put together the Brandywine exhibition of 28 pieces, says, "Those of us who are interested in antiques and historic preservation will find these appealing because they are pieces of history, part of the material culture of their age. They show their wear, they show their age right on the surface."

One of Burdan's favorites is the "Index horse," a beautifully minimal walking horse figure that got its name when it appeared in the Index of American Design - about 18,000 watercolor renderings of American decorative arts objects made before 1890. The 19th-century horse recalls early Chinese and Greek prototypes, yet looks as contemporary as a modern sculpture.

When buying an antique vane, its condition is as important a consideration as its form. Dealer Dennis Raleigh says, "Surface is everything. Each weather vane tells its own story."

Experts prefer vanes that retain much of their original gilded or painted surface. Over time, the objects develop a patina of age; never strip or polish an antique weather vane. (An informal breakfast and tour at the museum Saturday morning will include secrets held in the surfaces of weather vanes.)

As for form, there are eagles and peacocks, horses, whales, even butterflies and grasshoppers. Human forms bring a premium; collectors love Lady Liberty, angels, cherubs, and riders. Sailboats, railcars, and even early autos made an appearance in the 19th century.

Local antiques dealer Ed Hild of Olde Hope Antiques - his booth showcased many vanes during last month's Philadelphia Antiques Show - has determined that rare, full-bodied vanes hold their value, even through recession.

He's also seeing vanes in the "lower range" of prices - $5,000 to $18,000 - experience a revival.

"I think the appeal is universal. You see the older, more seasoned collectors looking at the rarest, and younger buyers coming into the market love the form," Hild says.

How much will those "seasoned collectors" pay? Five figures are the norm. Last year, Pook & Pook in Downingtown sold an elegant leaping stag with original patinated surface for $71,100, and a rare codfish vane brought $40,290.

The blockbuster price was $5.8 million, paid in 2006 for a molded copper Indian chief weather vane at a Sotheby's auction. Rare form and a great surface closed the deal, and Jerry Lauren of Polo Ralph Lauren was the buyer.

But you don't have to go back in time for the art.

Artist Karen Hurd of Lancaster County makes decorative arrow vanes, offered at the Brandywine River Museum Shop.

"Not everyone has the space to display a large, original weather vane," she says. "The whole purpose is to give someone a remnant of a popular design used in a different time period."

And perhaps show people which way the wind blows.