Claim: Illinois Caverns state natural area, featuring the Mommoth Cove of Illinois,  started its commercial operations in March 1901 and was sold to the State of Illinois in 1985 under Armin Krueger's management.
Evidence: It features Illinois Caverns which is alternatively known as Mammoth Cave of Illinois (also Burksville Cave, Egyptian Cave, Eckert Cave). What is now known as Illinois Caverns hosted its first paying customers in March 1901, operated by a Mr. White of East Saint Louis. When the cave and environs were sold to the State of Illinois in 1985, care of the site was entrusted to Armin Krueger, until his death.