Graham Cave State Park is a state park in the U.S. state of Missouri consisting of 369 acres located in Montgomery County. The park's namesake, Graham Cave, is a cave in St. Peter sandstone with an entrance 120 feet wide and 60 feet high and an extent of about 100 feet into the hillside. The cave protects an historically important Pre-Columbian archaeological site dating back to as early as 10,000 years ago.