Biloxi, Miss. ? On the great yawning porch that once belonged to Confederate President Jefferson Davis, two women sit in rockers listening to the cicadas and looking out over Mississippi Sound as they wait for their tour to begin.

Before Hurricane Katrina, some 200 people came each day to visit the house — the only structure on the oak-shaded Beauvoir estate not destroyed by the storm. And that’s just what’s needed to break even. Tourism has dropped off 20 percent here, with just a few visitors on some days since BP PLC’s well blew out in the Gulf of Mexico.

The story here is mirrored across the Gulf Coast. Beaches have been cleaned of crude, the leak has been plugged and some cities never had oil wash ashore at all. Still, tourists stay away from what they fear are oil-coated coastlines — a perception officials say could take years to overcome and cost the region billions of dollars.

“We had Katrina, then the recession and now we have the oil,” said Rick Forte, executive director of the Beauvoir estate. “It’s hard to overcome this when no one is coming.”

With the summer tourist season coming to a close after Labor Day weekend, destinations are scrambling to keep businesses afloat and hang on to the region’s 400,000 travel industry jobs. Some are trying discounts, special concerts and celebrity-endorsed commercials inviting residents to visit attractions once seen as havens for out-of-towners in their hometowns.

BP gave millions to the region for tourism promotion — $25 million to Florida and $15 million each to Louisiana, Mississippi and Alabama — though most of that money already has been spent with little effect.

“Once perceptions are formed, they take quite some time to change,” said Geoff Freeman, executive vice president of the U.S. Travel Association, a national nonprofit trade association. “One of the best examples was after Katrina — here we were in 2010 and we were only now ready to get to 2005 levels.”

The association commissioned a study by the Oxford Economics forecasting group that projected the disaster could cost the region $22.7 billion by 2013. With a $500 million infusion from BP to promote tourism, they estimated that figure could drop to $15.2 billion. The group also said travel to the Gulf Coast wouldn’t rebound until at least 2013.

Communities known for their beaches or charter fishing appear to have suffered most, while a few others managed unexpected increases after an anemic recession year.

In Alabama’s Dauphin Island, known for its sugar sand beaches and bird sanctuaries, 90 percent fewer people booked summer rentals compared to last summer, said Mayor Jeff Collier.

Other cities with more attractions showed increases over last year. New Orleans began 2010 as the country’s top tourist destination, said Kelly Schultz, vice president of the city’s Convention and Visitors Bureau. But after a flurry of news reports on the oil spill from New Orleans, officials spent much of the $5 million from BP assuring people oil wasn’t in their city, Schultz said.