The next time you go into a national park visitor center to buy a map, look at the person at the register. She or he won't be wearing the green and gray of a national park uniform; rather an employee of a cooperating association will be taking your money. In Great Smoky Mountains National Park, the Great Smoky Mountains Association, a membership organization, runs the visitor center bookstores and does a lot more.

"Cooperating Associations" were formed by the National Park Service and first run by government employees. But the government was not prepared to develop and provide educational content. From the first, visitors in national parks had questions such as, "What is that flower that I saw on the trail?" In 1923, the Yosemite Association was established as the nation's first cooperating association with the National Park Service. In the 1970s, associations broke away from the government. Now government employees cannot serve on association boards.

I've just been voted onto the board of the GSMA and I'm getting a first-hand look at how the association runs. Like all Cooperating Associations, GMSA is non-profit 501C3 organization, with an official agreement with the NPS to provide books, maps, and other educational materials on the Smokies and sell them in visitor centers. We work closely with the park and there's a great trust level between us - the GSMA office is across a small courtyard from the park headquarters.

However, part of the trust and great working relationship comes from the fact that we can't tell the Smokies staff how to run their national park. We're not an advocacy group and don't take positions on park issues as an association. This must have been difficult during the long, protracted North Shore Road issue, one where almost everyone favored a financial settlement rather than building another road through the park.

Terry Maddox, who has served as the association's executive director for 20 years, says "the park decides what projects they support. We try to help them."

When he came to GSMA, there were 595 members; now we have over 11,000 members and a budget of $7.5 million. All members get 15 percent off on anything they buy in visitor center stores and on the web. With a basic membership of $25, a membership quickly pays for itself. GSMA books and maps are not easily available in most other bookstores and are not sold on Amazon. So if you want Hiking Trails of the Smokies, the hiking bible describing every trail in the park - accept no substitution - you have to buy it from GSMA. In addition, with your GSMA discount card, you can get a discount in other park associations stores.

The Great Smoky Mountains Association currently publishes 38 books, and many nature trail booklets, maps and DVDs. Unlike commercial publishers, their books seldom go out of print. Mountain Makin's Cookbook, published in 1957, was the association's first book. It has been revised several times and still offered today. Probably the best-known publication from national park associations is the park newspaper, which comes out four times a year.

In addition to books and educational materials produced by GSMA, visitor centers in the Smokies sell other products, including my two hiking guides. A park committee votes on whether an item is appropriate to sell in the stores; it's a straight 'yes' or 'no' vote. There's always a concern that cooperating association not look like a commercial concession. So no People magazine or cans of Coke.

The sales also help out Great Smoky, as GSMA returns 17 percent of its gross income to the park. In return, the park doesn't charge rent.

Now, not all national parks have cooperating associations. For example, on the Blue Ridge Parkway, the bookstores are run by Eastern National. Eastern National was established in 1947 to partner with a number of small parks along the Eastern Seaboard that could not sustain their own associations. On the Parkway, Eastern National runs the visitor centers but doesn't publish any material. Cooperating associations are different from "friends groups," such as Friends of the Smokies. Their mission is to raise funds to support park projects.

GSMA runs nine visitor centers, four in the park and five outside the park, in buildings owned by various town chambers of commerce, such as Gatlinburg, Sevierville, and Pigeon Forge. In 2009, for the 75th anniversary of the Smokies, a tiny visitor center was opened at Dollywood, an amusement park with a country music theme owned by Dolly Parton. Though small, this location reaches people who may not think about going into the park at all.

Each visitor center has its own history. Sugarlands, close to Gatlinburg, was the only building built as a visitor center. Cades Cove Visitor Center, the second-highest grossing store, looks like an old country store but it's a modern building. Historically, Cades Cove didn't have country stores. The most challenging aspect of cooperating associations is getting enough square footage in the stores to display their items in an attractive manor.

In May, GSMA will open an information center at Clingmans Dome, making it the highest visitor center in the east. The information center will be located on the way up to the tower, in a remodeled bathroom building. New bathroom facilities will be built by the park in the Clingmans Dome parking lot. Since Clingmans Dome is the second-most visited section of the park, it ought to bring in a good income. And that's more money for the Great Smoky Mountains National Park.