National Park Guide: South Dakota's Wind Cave

— -- Mount Rushmore and its chiseled faces of presidents George Washington, Thomas Jefferson, Abraham Lincoln and Theodore Roosevelt is South Dakota's most recognizable feature. But go 41 miles south, and you'll find one of the reasons that earned Roosevelt a place there.

Roosevelt, a strong advocate for preserving America's wilderness, signed a law on Jan. 3, 1903, creating the Wind Cave National Park in South Dakota, one of five national parks established during his presidency.

Since then, the park has tripled in size, most recently with the addition of 5,555 acres of land last year that include a "buffalo jump" where early indigenous Americans are thought to have hunted bison.

The main feature is a cave 138 miles long, the world's fifth-longest known cave. White pioneers in the Black Hills made the first recorded discovery in 1881, but the cave's numerous passages, boasting most of the world's known boxwork formations, are still not fully explored.

"We're probably the most complex cave in the world," says Tom Farrell, the park's chief of interpretation.

Alma McAllister of Hot Springs, S.D., has been a frequent visitor since the late 1950s. McAllister, 85, has entered the cave just three times in all of her visits. She says it's nice, but she gets a little claustrophobic. She's attracted to the park's abundant wildlife and prairie ecosystem. "I want to see the elk and the buffalo," she says. "I keep track of when they were born. Our park is absolutely beautiful."

This summer, archaeologists will study the area around the buffalo jump, Farrell says. A carbon dating from the early 1970s found human activity at the site as early as the year 1030. A survey will also be done of native plants and historical buildings on the newly acquired 5,555 acres.

"We've got a lot going on this summer," Farrell says.

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About the park

Size: 33,851 acres

Visitors: 538,394 in 2011

Established: 1903

History: American Indians are thought to have known about the cave for centuries. But two pioneers made the first recorded discovery in 1881. Wind Cave was the first national park created to protect a cave.

When visiting: Address: 26611 U.S. Highway 385, Hot Springs, S.D. 57747. Visitor information: 605-745-4600.

Of note: At 138 miles, Wind Cave is the fifth-longest known cave in the world and features 95% of the world's known boxwork formations.

Ellis also reports for the Argus Leader in Sioux Falls, S.D.