TAHLEQUAH — Before a building, district, site, structure or object can be designated a National Historic Landmark, it must hold historical significance for the entire country.

National Park Service Heritage Partnership Programs Historical Architect Thomas Keohan defined a National Historic Landmark Wednesday as part of Oklahoma’s 24th annual Statewide Preservation Conference at the Tahlequah Armory Municipal Center.

“They are places that are found throughout America,” he said. “They’re in all of our communities, and they’re in all of our states and our territories in the United States. Each National Historic Landmark possesses a special quality that is unique and significant to the entire nation.”

In Native America, 21 such landmarks have been designated over the years. The state’s earliest include Fort Sill, which remains the only active fort used during the Indian wars on the south plains, and Fort Gibson, which was built in 1824 in the Indian Territory. Both were given the nod of national historic significance Dec. 12, 1960.

The most recent addition to Oklahoma’s list of NHLs is the Platt National Park Historic District, on land the Chickasaw Nation sold in 1902 to the federal government for park use. This site, in Sulphur, became nationally recognized July 7, 2011.

“Buildings may be the first thing you think of when you think of a National Historic Landmark, and in fact, most National Historic Landmarks are buildings,” said Keohan. “The Yuma Territorial Prison is an important survivor of the American westward expansion, and of course, the Boston Avenue Methodist Episcopal Church for its contribution to American architecture, among other things.”

The University of Oklahoma’s Bizzell Library, which became an NHL site Jan. 3, 2001, was the focus of a racial segregation Supreme Court case. Another state NHL that impacted how people co-exist is the Boley Historic District, an all-black town founded in 1903 as a product of segregationist policies.

The Boley Historic District, in Okfuskee County, became an NHL May 15, 1975. Another NHL site with historical significance because of human impact is Millerton’s Wheelock Academy, originally a missionary school for girls of the Choctaw Nation that became a model for academies developed by the Seminole, Cherokee, Chickasaw and Creek nations. Also on the list is Akin’s Sequoyah Cabin, which was the log cabin home where Sequoyah created the written language of the Cherokee people.

Keohan, who works out of the Intermountain Regional Office in Lakewood, Colo., said an NHL doesn’t have to have four walls and a roof to be historically significance.

“Sites include no buildings at all,” he said. “Sites are locations where historically significant events or activities took place. These sites include gardens, battlefields, archeological sites and even trails.”

An Oklahoma site that was the location of a major event is the Washita Battlefield, where George Custer led the Seventh Cavalry in a surprise attack on the village of Cheyenne Chief Black Kettle in 1868. The Washita Battlefield is near Cheyenne.

“Structures are another category of National Historic Landmarks,” Keohan said.

“These are basically constructions that are not used for human shelter. They include things like lighthouses, bridges, industrial complexes, ships and even more things than that. The Boston Lighthouse in Massachusetts is the location of the first lighthouse in America. And then Eads Bridge in St. Louis is significant because it was, at the time, the largest bridge of its kind, linking east- and west-running railroads.”

Keohan said districts are important as a group of buildings, rather than a particular building for its individual historic value.

“Historic districts could be communities, villages, towns or neighborhoods,” he said.

“Some National Historic Landmarks are well-known, like the Empire State Building in New York City,” said Keohan. “National Historic Landmarks are really a select group of America’s historic properties. Despite their relative rarity, they’re found in every state and U.S. territory. Fewer than 2,500 National Historic Landmarks exist, and that compares to over 80,000 or so nationally registered historic properties. So they are a select group. There are only about 20 to 25 landmarks that are nominated each year because they have to have significance to the entire nation.”