The Great Smoky Mountains and a Puerto Rican fortress made the cut, beating out Yosemite National Park, a St. Louis office building and the site of the Wright brothers' first flight.

It was the semifinal round of a sort of beauty pageant of the world's wonders--the U.S. competition for this year's nominations to the World Heritage list.

The American entrants, selected last month from 10 contenders by officials from nine federal agencies, will be sent on to the World Heritage Committee in Paris. There, representatives from 21 countries will judge the cultural and natural sites on their "outstanding universal value to mankind" and render their verdict by the fall of 1983.

Another U.S. nomination--the Cahokia Mounds, a prehistoric Indian site in Illinois--is still pending and could be added to the world list this fall. It would join 112 other wonders of the world, from Australia's Great Barrier Reef to the Pyramids of Giza to the Palace of Versailles.

The United States has nine properties on the world list: the Everglades, the Grand Canyon, Independence Hall, Redwood and Yellowstone national parks, Mammoth Cave National Park in Kentucky, Mesa Verde National Park in Colorado, Olympic National Park in Washington state and Wrangell-St. Elias National Park in Alaska.

Winning the World Heritage List seal of approval appears to be more a matter of status than substance, however, at least for properties in this country.

The World Heritage Committee was established in 1972 by the World Heritage Convention, a treaty to protect world resources proposed by the United States and now ratified by 63 countries.

Before a property can be added to the list, its sponsoring country must promise to take steps to make certain it will remain unspoiled.

In this country, however, the nine world-class properties are federally owned and already enjoy such protection. And Interior Department regulations require that any private or state-owned properties also must be protected adequately before they are nominated.

The World Heritage list is "almost an honors list" here, adding little to existing protections, said Robert Milne, chief of the National Park Service's international branch, which administers the program. "But there are other areas in the world where that's not the case," he said. The convention was designed "to identify these very special properties so that everybody knows that they deserve particular protection."

This year's U.S. nominees--Great Smoky Mountains National Park in Tennessee and North Carolina and La Fortaleza-San Juan National Historic Site in Puerto Rico--were chosen with an eye to geographic representation and political appeal, as well as natural beauty. The interagency committee, Milne said, wanted another eastern addition to the U.S. roster as well as an example of the country's Hispanic heritage.

Winning approval from the international committee isn't a sure-fire, rubber-stamp process. Committee representatives, in fact, can get downright finicky about what makes it onto their list, not to mention being strongly nationalistic.

Italy nominated the City of Rome, for example, and the committee turned thumbs-down on the Eternal City. "They said, 'What do you mean, the whole city?' " Milne said. "So the historical sites were identified and described and the restaurants between them were excluded," he said, and Rome made it on the list.

Thomas Alva Edison's laboratory in West Orange, N.J., didn't even make it to the full committee for review. It was headed off for promoting, as the awkward French translation put it, "the cult which is rendered this hero of modern science" and glorifying "the site of his social prominence rather than that of his initial successes" in Menlo Park.

The United States also withdrew its nomination of the site of the Wright brothers' historic flight at Kitty Hawk, N.C., rather than see it rejected. "The French have a tendency to say they had the first man-powered guided flight, and we don't know what the Russians think, but these are prideful points," Milne said. "We're sure the Wright brothers were the first, but we want that more thoroughly documented for the international forum to remove all chances of debate." The site finished in the top 10 this year, and thus stands a good chance of being nominated in the future.

By the time a vote on Kitty Hawk might arise, however, the United States may not be able to participate. Convention rules bar committee representatives from voting if their country has not donated money to the World Heritage Fund for two consecutive years. The United States didn't contribute to the fund this year, and no money is earmarked in the fiscal year 1983 budget.