 The Madison Limestone is one of Wyoming's most spectacular geological features, here where you can see it on the surface. However, it's where you can't see it, where the Madison formation is deep underground, where it makes its biggest contribution to Wyoming's economy. Here, where it outcrops on the slopes of our mountain ranges, porous Madison Limestone absorbs billions of gallons of fresh water. This water slowly percolates through the rock as gravity pulls it downhill into the geologic basins between the mountain ranges. In those deeply submerged rocks, the Madison becomes perhaps the most important aquifer or water-bearing strata in Wyoming. In this semi-arid region, many of our communities and industries depend upon groundwater pumped from the Madison formation. In other areas, including parts of the Wind River, Bighorn Basin, and the Alkric Mountains, oil and natural gas have moved upward into the Madison formation from underlying rocks. Drilling into the Madison has contributed considerable mineral wealth to Wyoming. Whether you'd like to admire the service manifestations of the Madison, drink the water, or burn the fossil fuel stored in it, the Madison is definitely one of Wyoming's most impressive features. From the University of Wyoming Extension, I'm Barton Stamm, Exploring the Nature of Wyoming.