Attendance hasn't been a roller coaster, it's just been up, up and up.

On Wednesday, Silverwood Theme Park will reach a record for annual attendance, with more than 600,000 guests.

That's up 6 percent compared with the 2009 season, said Nancy DiGiammarco, spokeswoman for the park. Last year was up 2 percent from 2008, she said.

Since the late '90s, Silverwood has grown its attendance, particularly in the last few years, when many other amusement parks suffered decreases in attendance.

"We're feeling wonderful about this year," DiGiammarco said. "No matter what the economy looks like, moms want kids to have fun vacations."

She said the theme park's advertising in the Seattle, Portland and Calgary markets provided a boost this year that helped the park reach the new levels. The park's message: "Affordable, family fun a short drive away," she said.

The image of a low-cost alternative to theme parks outside the Northwest sold well in those three markets, she said.

Also, the growth can be attributed to owner Gary Norton's continued investment in the park.

She said there has been talk of a new attraction next year, and there could be an announcement later this year detailing what that might be.

Scarywood also will continue to grow next year, she said.

Of the guests who visited the park in 2010, an estimated 400,000 were vacationers, which according to an updated Idaho Department Commerce study spent approximately $67.9 million in the Coeur d'Alene-Spokane region on services such as dining, shopping, hotel stays, gas and more, she said.

Silverwood announced that it will award visitor No. 600,000 a free 2011 season pass to the theme park.

Silverwood has been singled out for the role it plays in the Inland Northwest's economy, she said.

The former state tourism director for the Idaho Department of Commerce, Carl Wilgus, called Silverwood the "most attended attraction in the state," she said.