The following article describes a recent geophysical survey whose purpose was to locate a solution cavity known as the “Port Kennedy Bone Cave” beneath Valley Forge National Historical Park, in the carbonate belt of South-eastern Pennsylvania. The authors must apologize at the outset for presenting an article that leaves out such important details as the actual site location and coordinates or north arrows on the figures. This “if-we-tell-you-we-have-to-kill-you” approach is necessary because the bone cave contains one of the most important middle Pleistocene (Irvingtonian, or ∼750,000 year-old) fossil deposits in North America. It contains plants, insects, turtles, snakes, birds, and mammals—including giant tapirs, ground sloths, sabre-tooth cats, cheetahs, bears, and mammoths. Some of these fossils were new to science when the cave was discovered by quarry workers in the late 1800s, and were studied by the most famous paleontologists of that time (e.g. Edwin Drinker Cope, Henry C. Mercer, and Charles Wheatley). Some of the fossils from the bone cave are still found nowhere else. This makes the cave a possible target for modern looters if they are foolish enough to face the National Park Service Rangers, and the hazardous materials, and the rumored 150-ton locomotive, which protect its entrance…. But perhaps we should start at the beginning.