Graham Cave is located in Missouri

Graham Cave is a Native American archeological site near Mineola, Missouri in Montgomery County in the hills above the Loutre River. It is located in the 356 acre Graham Cave State Park. The entrance of the sandstone cave forms a broad arch 120 feet (37 m) wide and 16 feet (5 m) high. Extending about 100 feet (30 m) into the hillside, the cave protects an historically important Pre-Columbian achaeological site from the ancient Dalton and Archaic period dating back to as early as 10,000 years ago.

• http://en.wikipedia.org/wiki/Graham Cave