What cave found in New Mexico, is the second deepest cave in the continental US?

Lechuguilla Cave is, as of June 2013, with 138.3 miles (222.6 km) the seventh-longest explored cave in the world and the second deepest (1,604 feet or 489 meters) in the continental United States after the Tears of the Turtle Cave in the Bob Marshall Wilderness of Montana but it is most famous for its unusual geology, rare formations, and pristine condition.

In the 1950's, cavers heard wind roaring up from the rubble-choked cave floor. Although there was no obvious route, people concluded that cave passages lay below the rubble. Led by Dave Allured, a group of cavers from the Colorado Grotto gained permission from the National Park Service and began digging in 1984. Since the breakthrough into large walking passages occurred on May 26, 1986, explorers have mapped over 138 miles (222 km) of passages, making Lechuguilla the 7th longest cave in the world, and 4th longest in the United States. Lechugilla was also the deepest cave in the continental United States 1,604 feet (489 m) until the exploration of Tears of the Turtle Cave in 2014. Drawn by the cave's pristine condition and rare beauty, cavers come from around the world to explore and map its passages and geology.

Some of the bacteria strains isolated from the cave have been found to harbor novel pathways for antibiotic resistance. A 4 million year-old strain of Paenibacillus isolated from soil samples in Lechuguilla was found to be naturally resistant to many modern antibiotics, including daptomycin.