Residents of eastern Montana are justifiably proud of their "big sky" country. Its green-brown prairie, dotted by scrub and ponderosa pine, stretches in austere grandeur to a distant horizon. But the stark beauty of this region, into which cattle and sheep ranches comfortably blend, is now being threatened by America's insatiable appetite for energy.
The reason is coal. Beneath the prairie sod of Montana and the neighboring areas of Wyoming and North Dakota lie an estimated 1.3 trillion tons of coal and lignite40% of the U.S.'s reserves, enough to power American industry and heat American homes for decades. Moreover, since the Western...