Water from the Echo River surrounds Minnehaha Island, the site of the famed 1972 Flint Ridge-Mammoth Cave connection. 

Upon its 1941 national park designation, Mammoth Cave National Park was fairly esteemed for its beauty and extensive underground network.

However, it didn’t become today’s wildly renown behemoth until 1972, when a team of spelunkers discovered a connection to Mammoth Cave from a then-separate cave system. This officially crowned it as the longest cave system in the world, at 144.4 miles long.

“It really put us on the map,” said Molly Schroer, Mammoth Cave National Park public information officer. “It was realized just how significant our cave system’s resources are.”

This year marks the 50th anniversary of the discovery. Mammoth Cave and its mapping partner Cave Research Foundation are celebrating by offering four cave tours to the connection site on Sept. 9 and 10.

The four-hour, three-mile cave tours will focus on the history of Mammoth Cave exploration as participants traverse uneven and rocky terrain to reach the Mammoth Cave-Flint Ridge connection, as it is dubbed. While the tour is on the difficult side, it will not involve any crawling or climbing.

By 1972, the Mammoth Cave-Flint Ridge connection was decades in the making, said Karen Willmes, Cave Research Foundation eastern operations manager.

The Cave Research Foundation had been tirelessly mapping the Flint Ridge cave system since the 1940s, spending countless trips from different starting points, through different passageways, getting closer and closer to a breakthrough.

They knew that Mammoth Cave was close and understood the significance of a potential discovery.

“It consumed many years,” Willmes said. “The conditions had to be just right.”

Tight spots, muddy areas and high water proved obstacles to progress.

On the day of discovery, Willmes said the six Cave Research Foundation spelunkers had to make their way through a low spot – a “duck under” – where the water level reached just a few inches below the ceiling in order to reach the connection point.

Since the 1972 conjunction, further exploration has extended Mammoth Cave’s length to 420 miles. But there’s no end in sight. Some days, Cave Research Foundation spelunkers find 30 additional feet of unexplored cave tunnels; other days, they might uncover 100 feet, Willmes said.

“We haven’t found everything,” she said. “It’s not big discoveries, just little incremental bits that add to the cave. … It’s endless.”

Registration for the $35 “50th Anniversary Connection Tour” tickets opens Aug. 1 on Recreation.gov. There are 20 tickets available for each of the four tours, scheduled for 8:30 a.m. and 1:45 p.m. on Sept. 9 and Sept. 10. Participants must be over 16 and wear sturdy, lace-up hiking boots to be admitted.

Other celebratory events from Sept. 7-10 will include ranger-led evening programs highlighting the connection discovery and hands-on activities at the picnic area.

– Follow regional reporter Sarah Michels on Twitter @sarah_michels13 or visit bgdailynews.com.