Utah Mining Gazette
October 4 1873
pg. 46
Cumberland Gap Cave.
A correspondent, A. L. S., says in reference to this remarkable formation, described in our issue of September 13, that, after General Morgan's retreat from that spot, the cave was explored for a distance of four miles by Confederate soldiers, and a new opening was discoverd (sic), three miles from the one mentioned by H. B. N. The place has never been thoroughly investigated, but chambers, far surpassing in grandeur that described by our earler (sic) correspondent, have been found. In penetrating the rock, it is found that the new entrance leads for 6,000 yards through sandstone;d in an (sic [and in]) this section of the cave, vast quantities of human bones of gigantic size were found, some skulls being large enough to put on over a man's head (bold added). It is intended, during the current month, to throughly (sic) explore the cave.-Scientific American.
Correction ... more likely 1862 or 1863, following General Morgan's retreat on September 17, 1862. I suppose the Scientific American article could have been anytime between 1863 to September 1873.