Incident at Phantom Hill « Movie from 1966

At the end of the U.S. Civil War, a group of Southern rebels steal $1 million in gold from a Union shipment, stashing the loot in a cave near Phantom Hill, Texas.

When the group is captured by Union soldiers, the rebel leader agrees to reveal the location of the gold in exchange for his freedom, but things get complicated when the search party is ambushed on the way to the cave.